Add ability to suppress individual BuildCheck diagnostics

[JanKrivanek]

Context

BuildCheck doesn't have similar mechanism like #pragma warning disable for silencing the Roslyn analyzers.
This was decided to be out of scope for the V1 (https://github.com/dotnet/msbuild/blob/main/documentation/specs/BuildCheck/BuildCheck.md#out-of-scope).
With the limiting of the number of reports per Check (#10625) - users might get to a situation where they are unable to ignore unwanted diagnostics and see others.

Workaround

• The reports throtling should be opt-out able (via Trait?)
• In case of throttling, one can enable the rule in project per project - to prevent the throttling accross entire build

Note

This will need a design of how the suppressions will be performed and recognized (e.g. xml comments)

[KalleOlaviNiemitalo]

e.g. xml comments

Or processing instructions, if those are ignored by older versions of MSBuild.