Add DisableSentryNative build property

[maxkatz6]

This PR adds a new DisableSentryNative build property, allowing to opt-out from linking and using Sentry.Native on .NET 8+ builds. By default, DisableSentryNative is false, so old behavior is kept unchanged.

Two main changes of this PR:

1. DirectPInvoke/NativeLibrary are only set when DisableSentryNative is false.
2. SentryNative.IsAvailable returns false, if DisableSentryNative was set to true.

Runtime switches (RuntimeHostConfigurationOption and AppContext.TryGetSwitch) were used to pass build property to the runtime library. FeatureSwitchDefinition used should make this switch into a compile-time variable.

Closes #4102

NOTE: while it should work, I haven't tested the build yet. Need to figure out how to prepare a local build with native bits and everything included.

[jamescrosswell]

NOTE: while it should work, I haven't tested the build yet. Need to figure out how to prepare a local build with native bits and everything included.

@maxkatz6 the PR where @vaind added SentryNative.IsAvailable might be helpful to look at. There are some integration tests build in PowerShell in that PR that demonstrate at least the conditions for SentryNative being available:

• fix: incorrect use of SentryNative within a WASM app #3363

Your code is looking at a couple of different scenarios/variants within that, I imagine (when it's enabled/disabled).

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.64%. Comparing base (495e742) to head (6eb1020).
Report is 542 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Sentry/Platforms/Native/SentryNative.cs	33.33%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4107      +/-   ##
==========================================
- Coverage   75.73%   72.64%   -3.09%     
==========================================
  Files         357      444      +87     
  Lines       13466    15996    +2530     
  Branches     2671     3153     +482     
==========================================
+ Hits        10198    11621    +1423     
- Misses       2593     3561     +968     
- Partials      675      814     +139     

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