A recent PR (#77204) started to import C++ source locations into Swift.
This PR flips a switch so these locations are actually used more widely.
Now some of the diagnostic locations are changed, but they generally
improved the quality of the diagnostics, pointing out conformances
imported from Obj-C code right when they are declared.
When importing @compatibility_alias declarations check if underlying declaration
is generic and if so, forward generic environment and generic parameters (if any)
to newly created typealias declaration, otherwise there is going to be a mismatch
between type associated with typealias and its declaration which leads to crashes.
Resolves: rdar://problem/39849926
