[6.0] Use "resilient conformance" logic for deciding protocol dependencies involving Sendable

[DougGregor]

• Explanation: When compiling with library evolution and a pre-Swift 6.0 deployment target, a mismatch between the notion of resilience used for determining whether a protocol that inherits Sendable might need to be treated as "dependent" differed from how other parts of IR generation decided whether to conformance should be considered as resilient. The difference came when both the protocol and its conforming type are in the same module as the user. Switch over to the "is this conformance resilient?" query that takes into account such conformances.
• Scope: Affects binaries that use conformances of Sendable-conforming protocols, use library evolution, and are buil for deployment targets that predate Swift 6.0.
• Issues: rdar://136586922
• Original PRs: Use "resilient conformance" logic for deciding protocol dependencies involving Sendable #76707
• Risk: Low. This is further narrowing from [6.0.1] Fix ABI mismatch involving Sendable-refining non-resilient protocols and deployment targets #76384.
• Testing: Tested against an affected project, plus new tests
• Reviewer: @aschwaighofer

[DougGregor]

@swift-ci please test