[ILLink analyzer] Add analyzer support for feature checks

[sbomer]

Adds support for annotating static boolean properties with [FeatureCheckAttribute(typeof(RequiresDynamicCodeAttribute))], causing the property to be treated as a guard for analyzer warnings about the corresponding Requires attribute.

Adds two new warnings for:

• Invalid use of FeatureCheckAttribute applied to a non-static or non-bool property
• Implementation of the property doesn't obviously satisfy the "guard property" (it should return false whenever the guarded feature is disabled).

See #94625 for notes on the design.
See #96859 for the API proposal.

[ghost]

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Issue Details

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Adds support for annotating static boolean properties with [FeatureGuardAttribute(typeof(RequiresDynamicCodeAttribute))], causing the property to be treated as a guard for analyzer warnings about the corresponding Requires attribute.

Adds two new warnings for:

• Invalid use of FeatureGuardAttribute applied to a non-static or non-bool property
• Implementation of the property doesn't obviously satisfy the "guard property" (it should return false whenever the guarded feature is disabled).

See #94625 for notes on the design.

Author:	sbomer
Assignees:	-
Labels:	linkable-framework
Milestone:	-

[jtschuster]

Thank you!