Add features to DynamicJson

[annelo-msft]

A number of features remain to be added to `DynamicJson and related "JsonData" types:

P0 for GA:

• Finalize decisions on what exceptions to throw for different operations, per Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
• Finalize decisions on where to add == operators
  • Initial work done in https://github.com/annelo-msft/azure-sdk-for-net/tree/dynamicjson-optional-properties-backup
• Add validation that property names don't include the . character
• Add a custom implementation of RequestContent, and return it from a RequestContent.Create overload.
  • See RoundTripDynamicJson sample for details
• Support WriteTo with StandardFormat
• Finalize decision on what library to ship types in
• Clean up: Make sure we're using all disposable types
• Clean up: Make sure we've removed unnecessary constructor calls
• Clean up/perf improvement: https://github.com/Azure/azure-sdk-for-net/pull/35204/files#r1164766524
• Add test for WriteTo() validation

P1:

• ObjectDocument abstraction
• Look into Fix bug when serializing DynamicData in net461 #35930 (comment) re: perf
• Rough sketch of support for adding JSON Merge Patch functionality, per https://www.rfc-editor.org/rfc/rfc7386
  • When added, use this recommended style for refdoc formatting: Update doc comment per: Standardize exceptions thrown from DynamicData #35605 (comment)
• Debugger proxy
• Add [RequiresUnreferencedCode] attribute for AOT, per Move DynamicData into Azure.Core package #35777 (comment)
• Implement indexer on MutableJsonElement
• Implement equality (tests: EqualsHandlesStringsSpecial, EqualsForObjectsAndArrays)
• Enable optimizations, per:
  - Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
  - Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
  - Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
  - DynamicData array Length property #35974 (comment)
• Null checks (test: CanTestPropertyForNull)
  • See samples: [Draft for discussion] Preliminary updates to Confidential Ledger samples to use DynamicJson #33931 (comment)
  • Completed with Don't throw if a property is missing from DynamicJson, to allow for optional property checks #34026
• Provide options to configure case sensitivity of property lookup
  • See samples: [Draft for discussion] Preliminary updates to Confidential Ledger samples to use DynamicJson #33931 (comment)
• Add Dispose to dispose the inner JsonDocument
• Move MutableJsonDocument and MutableJsonElement out of the Dynamic namespace
• Add WriteToAsync() methods
• Implement object property enumeration (test: CanEnumerateObject)
• Make it possible to set DynamicJsonProperty.Value.
• Add cast from DynamicJson to MutableJsonDocument and MutableJsonElement for performance (to allow bypassing dynamic bindings)
• Enable cast to IDictionary
• Remove debug exception per Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
• Decide UX for handling float overflow/underflow (test: FloatOverflowThrows, FloatUnderflowThrows)
• Add tests for type validations per Don't throw if a property is missing from DynamicJson, to allow for optional property checks #34026 (comment)
• Decide whether to expose DynamicJson.ArrayEnumerator publicly, per Prototype moving JsonData to be backed by JsonDocument #33063 (comment)
• Consider adding Clone() to MutableJsonElement to support value semantics
• Support BindBinaryOperation in DynamicJson (e.g. += works)
• Support BindUnaryOperation in DynamicJson (e.g. ++ works)
• Allow caller to pass SerializationOptions to MutableJsonDocument.Parse(), respect these for any call to Serialize()
• Decide whether to implement API parity with JsonElement for MutableJsonElement
• Consider implementing IFormattable to allow callers to control the precision of numbers when converted to strings
  • See $ - string interpolation - format string output
  • Per @heaths idea, implement DeepEquals via IEqualityComparer<DynamicData> - see details in Add Equals to DynamicData #35733 (comment)
  • Can we remove DynamicDataOptions completely? Enable configuring dynamic behavior through client options #36887 (comment)

Bug fixes:

• Handle escaping correctly in serialization to RequestContent
  • Issue repro documented here: https://github.com/Azure/azure-sdk-for-net/blob/dynamicjson_feedback/samples/AppConfigDemo/RoundTripSample.cs#L98
• Pass casing options into child DynamicJson nodes

[annelo-msft]

This work is now being tracked by #37074