[6.2] Add lifetime dependencies on function types representing ~Escapable enum elements with ~Escapable payloads

[meg-gupta]

Explanation: Enum elements are represented as a function type. Enums can satisfy a protocol's static method constraint by defining a enum element with the same signature.

We do not infer lifetime dependence on function types related to EnumElementDecl. This results to source compatibility bugs in some cases since Optional is now conditionally ~Escapable. In the example below a protocol specifying a static some method ends up with a generated witness that does not have lifetime dependencies leading to illegible diagnostics.

public protocol OptionalType<Wrapped> {
    associatedtype Wrapped
    static func some(_ wrapped: Wrapped) -> Self
}

extension Optional: OptionalType {}

This PR adds lifetime dependencies for function types representative of EnumElementDecls.

Scope: Affects ~Escapable and conditionally ~Escapable types

Risk: Medium. New code is exercised in the type checker on all conditionally ~Escapable enums.

Main PR: #82354

Reviewer: @atrick

Testing: CI testing.

Issue: rdar://152104558

[meg-gupta]

@swift-ci test