[editorial] Remove implementation specific specification from metric API (open-telemetry#3890)

The api.md document specifies the Metric API, it does not defined the
OpenTelemetry defined implementations of this API. Remove or correct the
details within this API and leave it for the implementation
specification to define.

Importantly, the API is decoupled from implementation for a reason.
Third-party implementation may exists that OTel does not have domain
over. This document needs to written with that in mind.

Related to
open-telemetry#3171
and
open-telemetry#3071.

Author: MrAlias

CHANGELOG.md

@@ -13,6 +13,9 @@ release.
 
 ### Metrics
 
+- Remove implementation specific specification from metric API.
+  ([#3890](https://github.com/open-telemetry/opentelemetry-specification/pull/3890))
+
 ### Logs
 
 ### Resource

specification/metrics/api.md

@@ -103,9 +103,6 @@ the metrics API:
 
 `Meter`s can be accessed with a `MeterProvider`.
 
-In implementations of the API, the `MeterProvider` is expected to be the
-stateful object that holds any configuration.
-
 Normally, the `MeterProvider` is expected to be accessed from a central place.
 Thus, the API SHOULD provide a way to set/register and access a global default
 `MeterProvider`.
@@ -599,9 +596,9 @@ language idiomatic name(s), for example `CreateUInt64ObservableCounter`,
 `CreateDoubleObservableCounter`, `CreateObservableCounter<UInt64>`,
 `CreateObservableCounter<double>`.
 
-It is highly recommended that implementations use the name `ObservableCounter`
-(or any language idiomatic variation, e.g. `observable_counter`) unless there is
-a strong reason not to do so. Please note that the name has nothing to do with
+It is highly recommended that the name `ObservableCounter` (or any language
+idiomatic variation, e.g. `observable_counter`) be used unless there is a
+strong reason not to do so. Please note that the name has nothing to do with
 [asynchronous
 pattern](https://en.wikipedia.org/wiki/Asynchronous_method_invocation) and
 [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern).
@@ -922,9 +919,9 @@ idiomatic name(s), for example `CreateUInt64ObservableGauge`,
 `CreateDoubleObservableGauge`, `CreateObservableGauge<UInt64>`,
 `CreateObservableGauge<double>`.
 
-It is highly recommended that implementations use the name `ObservableGauge`
-(or any language idiomatic variation, e.g. `observable_gauge`) unless there is
-a strong reason not to do so. Please note that the name has nothing to do with
+It is highly recommended that the name `ObservableGauge` (or any language
+idiomatic variation, e.g. `observable_gauge`) be used unless there is a strong
+reason not to do so. Please note that the name has nothing to do with
 [asynchronous
 pattern](https://en.wikipedia.org/wiki/Asynchronous_method_invocation) and
 [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern).
@@ -1165,10 +1162,10 @@ decide the language idiomatic name(s), for example
 `CreateObservableUpDownCounter<UInt64>`,
 `CreateObservableUpDownCounter<double>`.
 
-It is highly recommended that implementations use the name
-`ObservableUpDownCounter` (or any language idiomatic variation, e.g.
-`observable_up_down_counter`) unless there is a strong reason not to do so. Please
-note that the name has nothing to do with [asynchronous
+It is highly recommended that the name `ObservableUpDownCounter` (or any
+language idiomatic variation, e.g. `observable_up_down_counter`) be used unless
+there is a strong reason not to do so. Please note that the name has nothing to
+do with [asynchronous
 pattern](https://en.wikipedia.org/wiki/Asynchronous_method_invocation) and
 [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern).