ObjC methods include a +/- prefix to indicate if they are a class or
instance method. This information is valuable, and must be included in
the navigator generated by ExtractAPI.

rdar://150870936

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.

Resolves rdar://140298287

ExtractAPI's support for printing Objective-C category extensions from
other modules emits symbol graphs with an
`ExtendedModule@HostModule.symbols.json`. However, this is backwards
from existing symbol graph practices, causing issues when these symbol
graphs are consumed alongside symbol graphs generated with other tools
like Swift. This PR flips the naming scheme to be in line with existing
symbol graph tooling.

See
https://discourse.llvm.org/t/rfc-deprecate-and-eventually-remove-renderscript-support/81284
for the RFC

Extension SGFs require the module system to be enabled in order to discover which module defines the extended external type.
This patch ensures the following:
- Associate symbols with their top level module name, and that only top level modules are considered as modules for emitting extension SGFs.
- Ensure we don't drop macro definitions that came from a submodule. To this end look at all defined macros in `PPCalbacks::EndOfMainFile` instead of relying on `PPCallbacks::MacroDefined` being called to detect a macro definition.

Add back missing includes and revert revert "[clang][ExtractAPI] Stop
dropping fields of nested anonymous record types when they aren't
attached to variable declaration (#104600)"

This reverts commit c60da1a271a6bb271e7703b2f7c71fbece67ab78.

- Introduce primitives for removing records from `APISet` and managing
the record chain of `RecordContext`
- Detect nested anonymous record types and remove them from the `APISet`
after they have been fully traversed and transfer ownership of child
records to the parent context (if any)

rdar://133533830

Additionally this computes availability information for all platforms
ahead of possibly introducing a flag to enable this behavior.

rdar://123513706