[TypeChecker] Avoid checking lazy property accessors if they haven't been synthesized yet
Ttheir availability is going to match the property itself.
This is a workaround for lazy type-checking because synthesis
of accessors for such properties requires a reference to
`self` which won't be available because pattern binding
for the variable was skipped.
Resolves: rdar://129359362
Resolves: rdar://159463230
Resolves: https://github.com/swiftlang/swift/issues/84041
(cherry picked from commit 6e7de5c1e035e64d0da9e7f39e6454c41260ad3e)