- try_emplace(Key) is shorter than insert({Key, nullptr}).
- try_emplace performs value initialization without value parameters.
- We overwrite values on successful insertion anyway.

* Translate the following versions to 26.
  * watchOS 12 -> 26
  * visionOS 3 -> 26
  * macos 16 -> 26
  * iOS 19 -> 26
  * tvOS 19 -> 26

* Emit diagnostics, but allow conversion when clients attempt to use
invalid gaps in OS versioning in availability.

* For target-triples, only allow "valid" versions for implicit
conversions.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

try_emplace value-initializes values, so we do not need to pass
nullptr to try_emplace when the value types are raw pointers or
std::unique_ptr<T>.

RPaths are basically search paths for how to load dependent libraries.
The order they appear is the order the linker will search, we should
preserve that order in tbd files.

* Additionally add this level of detection to llvm-readtapi.

resolves: rdar://145603347

* Have clang always append & pass System/Library/SubFrameworks when determining default sdk search paths.
* Teach clang-installapi to traverse there for framework input.
* Teach llvm-readtapi that the library files (TBD or binary) in there should be considered private.

resolves: rdar://137457006

This would lead to a malformed TBD file.