Remove bunch of allocations caused by static arrays by favoring ReadOnlySpan<T>

[h3xds1nz]

Description

Fixes unnecessary allocations on static readonly arrays by refactoring them as ReadOnlySpans<T> of primitive types.
This under the hood allows references in runtime to the data directly as stored in the mapped file, not requiring any runtime allocs. See RuntimeHelpers.CreateSpan<T> intrinsic for more info. In most cases the value is then inlined directly into the method, saving memory references as well.

In other cases, such as the Geometry classes, it allows us to reference data directly without any pinning (fixed is then merely used to retrieve the pointer that's passed to the unsafe method.

This also removes some unoptimized foreaches as replacement for IndexOf/Contains (guess that's coming from very early in the days).

In the end, it also removes inefficient foreach and IndexOf replacements for Contains methods with ROS<char>.Contains(value).

Method	Mean	Error	StdDev	Allocated
ReadOnlySpan_Contains	1.118 ns	0.0111 ns	0.0098 ns	-
Original_Foreach_Contains	10.343 ns	0.0543 ns	0.0508 ns	-

Customer Impact

Improved performance, decreased allocations.

Regression

None.

Testing

Build and standard use. Should be easy to CR.

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[h3xds1nz]

I had to remove the optimization in PresentationBuildTasks as it still targets .NET Framework 4.7.2 and the build then fails.

[singhashish-wpf]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[anjali-wpf]

Thanks for your contribution.

[h3xds1nz]

Thanks @anjali-wpf for including it.