RUMM-2713: Move global RUM context into generic feature context storage

[0xnm]

What does this PR do?

This change removes global RUM context from GlobalRum singleton by moving it to the feature's context (DatadogContext#featuresContext).

Now RUM context will be stored in the generic dictionary Map<String, Any?> and can be accessed either by calling DatadogContext#featuresContext or by calling SdkCore#getFeatureContext.

Also SdkCore#setFeatureContext is removed in the favour of SdkCore#updateFeatureContext method which gives a mutable dictionary for the update, final update is thread-safe.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

Merging #1146 (ad1cf8a) into feature/sdkv2 (c484bd6) will increase coverage by 0.07%.
The diff coverage is 90.14%.

@@                Coverage Diff                @@
##           feature/sdkv2    #1146      +/-   ##
=================================================
+ Coverage          82.43%   82.50%   +0.07%     
=================================================
  Files                350      350              
  Lines              11524    11559      +35     
  Branches            1957     1980      +23     
=================================================
+ Hits                9499     9536      +37     
+ Misses              1424     1419       -5     
- Partials             601      604       +3     

Impacted Files	Coverage Δ
...c/main/kotlin/com/datadog/android/rum/GlobalRum.kt	42.11% <0.00%> (-21.72%)	⬇️
...android/v2/core/internal/DatadogContextProvider.kt	81.54% <0.00%> (-2.04%)	⬇️
...og/android/v2/core/internal/NoOpContextProvider.kt	3.45% <0.00%> (-0.12%)	⬇️
...otlin/com/datadog/android/tracing/AndroidTracer.kt	94.03% <71.43%> (-2.89%)	⬇️
...iew/internal/rum/WebViewRumEventContextProvider.kt	87.50% <75.00%> (-12.50%)	⬇️
.../kotlin/com/datadog/android/v2/core/DatadogCore.kt	89.50% <83.33%> (+0.10%)	⬆️
.../android/rum/internal/domain/scope/RumViewScope.kt	96.56% <90.32%> (+0.01%)	⬆️
...android/log/internal/domain/DatadogLogGenerator.kt	97.32% <100.00%> (+0.93%)	⬆️
...lin/com/datadog/android/rum/internal/RumFeature.kt	93.14% <100.00%> (+0.14%)	⬆️
.../datadog/android/rum/internal/domain/RumContext.kt	97.37% <100.00%> (+7.37%)	⬆️
... and 19 more

[mariusc83]

why are we doing this only for the RUM feature name ?

[0xnm]

Because context which is received by DatadogPlugin contains only RUM-related info, so it makes sense to update it only when RUM context is updated.

Anyway, DatadogPlugin will be removed in v2. This code won't live long.

[mariusc83]

LGTM