Remove allocations in BaseUriHelper, improve resource resolution performance

[h3xds1nz]

Currently blocked by #9822, hence draft.

Description

Optimizes methods in BaseUriHelper, removes most of the allocations directly in this class and opens up more optimization possibilities; directly builds upon #9739 and #9822.

• Removes IsSameKeyToken from SecurityHelper in favour of ReflectionUtils.IsSamePublicKeyToken.
• BaseUriHelper.GetAssemblyNameAndPart is now fully allocation free.
  • This allows for more optimizations in the future and already makes some paths without any allocations.
  • Instead of returning 3 strings, we return slices in AssemblyPackageInfo ref struct.
• In FontResourceCache, we can now use AlternateLookup to benefit from this change as well.
• BaseUriHelper.BaseUri was never set outside static constructor, where it was initialized to the s_packAppBaseUri value,
  hence I've removed the property altogether, which also led to removal of BindUriHelper.BaseUri which was just proxy.
• Code under CF_Envelope_Activation_Enabled macro was removed, most of the code is already missing in .NET Core than what was in reference files for .NET 3.5 and it is never compiled on NetFX nor on .NET Core.
• Changes in GetLoadedAssembly bring a bit of an improvement but there's more benchmarking needed on how to handle this chain most efficiently, so keeping as it is right now.

Cherry-picking some cases:

GetAssemblyNameAndPart

Method	someUri	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Allocated [B]
Original	/Mic(...)xaml [103]	104.95 ns	2.274 ns	6.706 ns	0.0448	752 B
PR__EDIT	/Mic(...)xaml [103]	45.42 ns	0.475 ns	0.445 ns	-	-

AssemblyMatchesKeyString vs ComparePublicKeyTokens

Method	someAssembly	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Allocated [B]
Original	Syste(...)7798e [89]	40.755 ns	0.3990 ns	0.3537 ns	0.0019	32 B
PR__EDIT	Syste(...)7798e [89]	8.135 ns	0.0835 ns	0.0740 ns	-	-

Customer Impact

Improved performance, decrased allocations.

Regression

No.

Testing

Local build, some assert testing; I'll provide tests before this goes out of draft.

Risk

Low to medium, there are quite a few changes but most of them are rather straightforward.

Microsoft Reviewers: Open in CodeFlow