Add some missing info to the SDKv2 upgrade guide.

We missed some sections and have some new sections that needed to be
added to the upgrade guide to v2 of the SDK.

Closes hashicorp/terraform-plugin-sdk#493.

Closes hashicorp/terraform-plugin-sdk#492.

Closes hashicorp/terraform-plugin-sdk#487.

Closes hashicorp/terraform-plugin-sdk#484.

Author: paddycarver

content/source/docs/extend/guides/v2-upgrade-guide.html.md

@@ -44,12 +44,16 @@ Upgrade topics:
 * [More Robust Validation of `helper/resource.TestCheckResourceAttrPair`](#more-robust-validation-of-helper-resource-testcheckresourceattrpair)
 * [More Robust Validation of Test Sweepers](#more-robust-validation-of-test-sweepers)
 * [Deprecation of `helper/schema.ExistsFunc`](#deprecation-of-helper-schema-existsfunc)
+* [Deprecation of `helper/schema.SchemaValidateFunc`](#deprecation-of-helper-schema-schemavalidatefunc)
 * [Removal of `helper/mutexkv` Package](#removal-of-helper-mutexkv-package)
 * [Removal of `helper/pathorcontents` Package](#removal-of-helper-pathorcontents-package)
 * [Removal of `httpclient` Package](#removal-of-httpclient-package)
 * [Removal of `helper/hashcode` Package](#removal-of-helper-hashcode-package)
 * [Removal of the `acctest` Package](#removal-of-the-acctest-package)
 * [Removal of the `terraform.ResourceProvider` Interface](#removal-of-the-terraform-resourceprovider-interface)
+* [Removal of the `helper/schema.Provider.StopContext` method](#removal-of-the-helper-schema-provider-stopcontext-method)
+* [Removal of `helper/schema.ResourceData.SetPartial`](#removal-of-helper-schema-resourcedata-setpartial)
+* [Removal of the `helper/schema.Provider.MetaReset` property](#removal-of-the-helper-schema-provider-metareset-property)
 * [Removal of Deprecated Validation Functions](#removal-of-deprecated-validation-functions)
 * [Removal of `helper/schema.Schema.PromoteSingle`](#removal-of-helper-schema-schema-promotesingle)
 * [Removal of `helper/schema.ResourceData.UnsafeSetFieldRaw`](#removal-of-helper-schema-resourcedata-unsafesetfieldraw)
@@ -335,6 +339,18 @@ twice. Providers should check for Not Found responses in Read, and call
 `helper/schema.ResourceData.SetId(“”)` and return no errors if a Not Found
 response is encountered, instead.
 
+## Deprecation of `helper/schema.SchemaValidateFunc`
+The `helper/schema.SchemaValidateFunc` type and the properties that use it,
+including `helper/schema.Schema.ValidateFunc`, are now deprecated in favor of
+`helper/schema.SchemaValidateDiagFunc`, which gains awareness for diagnostics,
+allowing more accurate errors to be returned.
+
+The `helper/validation` helper functions will have
+`helper/schema.SchemaValidateDiagFunc` equivalents of the validation functions
+added in a future release to ease the transition. Until that point, a 
+wrapper can be used that wraps the warnings and errors returned from
+`helper/schema.SchemaValidateFunc` in a `diag.Diagnostics`.
+
 ## Removal of `helper/mutexkv` Package
 The `helper/mutexkv` package provided convenience helpers for managing
 concurrency, but is not specifically related to Terraform plugin development,
@@ -509,6 +525,36 @@ this will involve changing the returned type of the `Provider()` function, and
 removing some type assertions; all necessary changes should be raised at
 compile time.
 
+## Removal of the `helper/schema.Provider.StopContext` method
+
+The `helper/schema.Provider.StopContext` method has been removed as its
+implementation has been reconfigured. Use `helper/schema.StopContext`, passed a
+`context.Context` originate from one of the new context-aware functions,
+instead.
+
+## Removal of `helper/schema.ResourceData.SetPartial`
+
+The `helper/schema.ResourceData.SetPartial` method was deprecated and has been
+removed. This method used to allow setting certain fields in state when
+`helper/schema.ResourceData.Partial` was set to `true`, but developers weren't
+clear under which circumstances that needed to happen.
+
+This method should never need to be used. `helper/schema.ResourceData.Partial`
+should be set to `true` before returning an error if the error should prevent
+any state from being part of the config being automatically persisted in state.
+For most providers, this doesn't matter, as the refresh step will take care of
+setting the state to what it should be.
+
+See [issue #476](https://github.com/hashicorp/terraform-plugin-sdk/issues/476)
+for more information.
+
+## Removal of the `helper/schema.Provider.MetaReset` property
+
+The `helper/schema.Provider.MetaReset` property allowed providers to set a
+function tha would be called during testing to reset the `meta` associated with
+the provider. This function was never actually called, and so the property has
+been removed.
+
 ## Removal of Deprecated Validation Functions
 The following `helper/validation` functions have been renamed, and the
 deprecated aliases have been removed:
@@ -566,11 +612,9 @@ their use case, and we can help find a path forward.
 
 * `helper/acctest.RemoteTestPrecheck`
 * `helper/acctest.SkipRemoteTestsEnvVar`
-* `helper/resource.EnvLogPathMask`
 * `helper/resource.GRPCTestProvider`
 * `helper/resource.LogOutput`
 * `helper/resource.Map`
-* `helper/resource.TestEnvVar`
 * `helper/resource.TestProvider`
 * `helper/schema.MultiMapReader`
 * `helper/schema.Provider.Input`
@@ -614,6 +658,7 @@ their use case, and we can help find a path forward.
 * `plugin.UIOutputServer`
 * `plugin.VersionedPlugins no longer has a "provisioner" key`
 * `resource.RunNewTest`
+* `resource.TestDisableBinaryTestingFlagEnvVar`
 * `schema.Backend`
 * `schema.FromContextBackendConfig`
 * `schema.SetProto5`