util-stats: Deprecate methods on the MetricBuilder API

Problem

We use MetricBuilder as or source-of-truth representation of a metrics
identity. However, it also has a `StatsReceiver` as a field that kind of
messes up this clean representation.

Solution

Deprecate the `statsReceiver` field and remove the metric instantiation
methods.

Differential Revision: https://phabricator.twitter.biz/D862244

Author: Bryce Anderson

CHANGELOG.rst

@@ -42,6 +42,13 @@ Breaking API Changes
 
 * util-core: The `c.t.util.Responder` trait has been removed. ``PHAB_ID=D824830``
 
+Deprecations
+~~~~~~~~~~~~
+
+* util-stats: Deprecated methods on `MetricBuilder` for directly instantiating metrics so that we can
+  eventually remove the `statsReceiever` field from `MetricBuilder` and let it just be the source of
+  truth for defining a metric. ``PHAB_ID=D862244``
+
 22.1.0
 ------
 

util-stats/src/main/scala/com/twitter/finagle/stats/MetricBuilder.scala

@@ -182,6 +182,7 @@ class MetricBuilder private (
   val percentiles: IndexedSeq[Double],
   val isStandard: Boolean,
   val metricType: MetricType,
+  @deprecated("Being removed to make MetricBuilder strictly a metric definition.", "2022-03-28")
   val statsReceiver: StatsReceiver)
     extends Metadata {
 
@@ -306,6 +307,7 @@ class MetricBuilder private (
    * Produce a counter as described by the builder inside the underlying StatsReceiver.
    * @return the counter created.
    */
+  @deprecated("Use the StatsReceiver interface for instantiation.", "2022-03-28")
   @varargs
   final def counter(name: String*): Counter = {
     this.statsReceiver.validateMetricType(this, CounterType)
@@ -316,6 +318,7 @@ class MetricBuilder private (
    * Produce a gauge as described by the builder inside the underlying StatsReceiver.
    * @return the gauge created.
    */
+  @deprecated("Use the StatsReceiver interface for instantiation.", "2022-03-28")
   final def gauge(name: String*)(f: => Float): Gauge = {
     this.statsReceiver.validateMetricType(this, GaugeType)
     this.statsReceiver.addGauge(this.withName(name: _*))(f)
@@ -326,6 +329,7 @@ class MetricBuilder private (
    * This API is for Java compatibility
    * @return the gauge created.
    */
+  @deprecated("Use the StatsReceiver interface for instantiation.", "2022-03-28")
   @varargs
   final def gauge(f: Supplier[Float], name: String*): Gauge = {
     this.statsReceiver.validateMetricType(this, GaugeType)
@@ -336,6 +340,7 @@ class MetricBuilder private (
    * Produce a histogram as described by the builder inside the underlying StatsReceiver.
    * @return the histogram created.
    */
+  @deprecated("Use the StatsReceiver interface for instantiation.", "2022-03-28")
   @varargs
   final def histogram(name: String*): Stat = {
     this.statsReceiver.validateMetricType(this, HistogramType)