[Feature Request] Suppress Codecov indirect coverage changes reports

[filzrev]

Is your feature request related to a problem? Please describe.
When PR is created.
Codecov randomly reports indirect coverage changes.
relating to following two files.

• https://app.codecov.io/gh/dotnet/docfx/pull/9056/blob/src/Docfx.Common/Git/GitUtility.cs
  -> It seems test is executed under detached head source randomly?
• https://app.codecov.io/gh/dotnet/docfx/pull/9056/blob/src/Docfx.YamlSerialization/Helpers/ArrayDictionary.cs
  -> It seems related test is not called or failed collect coverage data?

Describe the solution you'd like

I can't determine what's cause these coverage problems on CI environment.
Simple solution is to add following attribute to methods that cause coverage diff.

[ExcludeFromCodeCoverage(Justification = "When running CI Build. Codecov report Indirect changes.")]

[filzrev]

GitUtility.cs related indirect changes are suppressed by explicitly set ExcludeFromCodeCoverage.

ArrayDictionary.cs related indirect changes seems occurred by parallel execution.
If set maxParallelism to 1. This branch is not called.

On GitHub hosted runner. there are 2 CPU core. so race condition occurred occasionally.
On local environment. double-checked locking's lock wait is frequently occurs.
Thought it is not spend large lock-wait times. It might be better to optimize ArrayDictionary.cs code to lock-free.