Spec compliance matrix: C++ Declarative Configuration (#4720)

Fixes #

## Changes

Please provide a brief description of the changes here.

* Spec compliance matrix: C++ now supports Declarative Configuration:
* [Cpp issue
](open-telemetry/opentelemetry-cpp#2481)

For non-trivial changes, follow the [change proposal
process](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CONTRIBUTING.md#proposing-a-change).

* [ ] Related issues #
* [ ] Related [OTEP(s)](https://github.com/open-telemetry/oteps) #
* [ ] Links to the prototypes (when adding or changing features)
* [ ]
[`CHANGELOG.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CHANGELOG.md)
file updated for non-trivial changes
* [X] [Spec compliance
matrix](https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix/template.yaml)
updated if necessary

Author: marcalff

spec-compliance-matrix.md

@@ -291,19 +291,19 @@ Disclaimer: Declarative configuration is currently in Development status - work
 
 | Feature | Go | Java | JS | Python | Ruby | Erlang | PHP | Rust | C++ | .NET | Swift |
 | ------- | -- | ---- | -- | ------ | ---- | ------ | --- | ---- | --- | ---- | ----- |
-| `Parse` a configuration file | + | + | + |  |  |  | + |  |  |  |  |
-| The `Parse` operation accepts the configuration YAML file format | + | + | + |  |  |  | + |  |  |  |  |
-| The `Parse` operation performs environment variable substitution | + | + |  |  |  |  | + |  |  |  |  |
-| The `Parse` operation returns configuration model | + | + | + |  |  |  | + |  |  |  |  |
-| The `Parse` operation resolves extension component configuration to `properties` |  | + |  |  |  |  | + |  |  |  |  |
-| `Create` SDK components | + | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation accepts configuration model | + | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation returns `TracerProvider` | + | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation returns `MeterProvider` | + | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation returns `LoggerProvider` | + | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation returns `Propagators` |  | + |  |  |  |  | + |  |  |  |  |
-| The `Create` operation calls `CreatePlugin` of corresponding `ComponentProvider` when encountering extension components |  | + |  |  |  |  | + |  |  |  |  |
-| Register a `ComponentProvider` |  | + |  |  |  |  | + |  |  |  |  |
+| `Parse` a configuration file | + | + | + |  |  |  | + |  | + |  |  |
+| The `Parse` operation accepts the configuration YAML file format | + | + | + |  |  |  | + |  | + |  |  |
+| The `Parse` operation performs environment variable substitution | + | + |  |  |  |  | + |  | + |  |  |
+| The `Parse` operation returns configuration model | + | + | + |  |  |  | + |  | + |  |  |
+| The `Parse` operation resolves extension component configuration to `properties` |  | + |  |  |  |  | + |  | + |  |  |
+| `Create` SDK components | + | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation accepts configuration model | + | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation returns `TracerProvider` | + | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation returns `MeterProvider` | + | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation returns `LoggerProvider` | + | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation returns `Propagators` |  | + |  |  |  |  | + |  | + |  |  |
+| The `Create` operation calls `CreatePlugin` of corresponding `ComponentProvider` when encountering extension components |  | + |  |  |  |  | + |  | + |  |  |
+| Register a `ComponentProvider` |  | + |  |  |  |  | + |  | + |  |  |
 
 ## Exporters
 

spec-compliance-matrix/cpp.yaml

@@ -500,31 +500,31 @@ sections:
   - name: Declarative configuration
     features:
       - name: '`Parse` a configuration file'
-        status: '?'
+        status: '+'
       - name: The `Parse` operation accepts the configuration YAML file format
-        status: '?'
+        status: '+'
       - name: The `Parse` operation performs environment variable substitution
-        status: '?'
+        status: '+'
       - name: The `Parse` operation returns configuration model
-        status: '?'
+        status: '+'
       - name: The `Parse` operation resolves extension component configuration to `properties`
-        status: '?'
+        status: '+'
       - name: '`Create` SDK components'
-        status: '?'
+        status: '+'
       - name: The `Create` operation accepts configuration model
-        status: '?'
+        status: '+'
       - name: The `Create` operation returns `TracerProvider`
-        status: '?'
+        status: '+'
       - name: The `Create` operation returns `MeterProvider`
-        status: '?'
+        status: '+'
       - name: The `Create` operation returns `LoggerProvider`
-        status: '?'
+        status: '+'
       - name: The `Create` operation returns `Propagators`
-        status: '?'
+        status: '+'
       - name: The `Create` operation calls `CreatePlugin` of corresponding `ComponentProvider` when encountering extension components
-        status: '?'
+        status: '+'
       - name: Register a `ComponentProvider`
-        status: '?'
+        status: '+'
   - name: Exporters
     features:
       - name: '[Exporter interface](specification/trace/sdk.md#span-exporter)'