[Compile Time Constant Extraction] Query nominal type *conformances* to get at the protocols, instead of getAllProtocols().

[artemcm]

As it stands, for extension macros which add protocol conformances, the list of protocols specified on the macro's conformances: parameter gets added in its entirety to the list of a nominal type's protocols in ConformanceLookupTable::addMacroGeneratedProtocols. Whereas the macro itself, may only add some of the specified conformances. This means that getAllProtocols() may contain a super-set of protocols captured in getAllConformances, some of which may not actually be generated by the macro.

This change narrowly fixes ConstExtract to query actual generated conformances. Though, potentially we should make ConformanceLookupTable::addMacroGeneratedProtocols behave in a way that reflects the protocols the macro actually adds the conformances to, instead of the ones it may add conformances to.

Resolves rdar:https://130316531

[artemcm]

@hborla, @slavapestov
From https://github.com/swiftlang/swift-evolution/blob/main/proposals/0402-extension-macros.md#suppressing-redundant-conformances:

The following restrictions apply to generated conformances and names listed in @attached(extension):

• An extension macro cannot add a conformance to a protocol that is not covered by the conformances: list in @attached(extension, conformances:).
• An extension macro cannot add a member that is not covered by the names: list in @attached(extension, names:).
• An extension macro cannot introduce an extension with an attached peer macro, because the peer-macro-generated names are not covered by the original @attached(extension) attribute.

It is my reading of this that there is no reason that the macro may choose to conditionally avoid adding a conformance to a protocol specified in conformances:. In which case, should addMacroGeneratedProtocols add them all unconditionally?

[artemcm]

@swift-ci test