[5.5-05142021][ConstraintSystem] Detect passing sync closure to async argument early

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Cherry-pick of (main) #37430, (5.5) #37479

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• Explanation:

This helps in situations where there are multiple overloads which
differ only in async effect of their parameters. Passing sync argument
to a sync parameter is always preferred and when detected early
allows solver to avoid some of the duplicate work re-solving for
the rest of the path e.g.

func test<T>(_: () -> T) {}
func test<T>(_: () async -> T) {}

test {
  // sync work
}.op(...)

In this case since closure is synchronous first overload of test
is always preferred (when it's a match) and solver can skip re-checking
body of the closure and op call when it encounters async version.

• Scope: Passing a sync closure to a call that has two overloads that differ only in async for one or more arguments.

• Main Branch PR: [ConstraintSystem] Detect passing sync closure to async argument early #37430

• Resolves: rdar://77942193

• Risk: Low

• Reviewed By: @hborla

• Testing: Regression tests added to the suite

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@swift-ci please test