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.

Currently BlockAddresses store both the Function and the BasicBlock they
reference, and the BlockAddress is part of the use list of both the
Function and BasicBlock.

This is quite awkward, because this is not really a use of the function
itself (and walks of function uses generally skip block addresses for
that reason). This also has weird implications on function RAUW (as that
will replace the function in block addresses in a way that generally
doesn't make sense), and causes other peculiar issues, like the ability
to have multiple block addresses for one block (with different
functions).

Instead, I believe it makes more sense to specify only the basic block
and let the function be implied by the BB parent. This does mean that we
may have block addresses without a function (if the BB is not inserted),
but this should only happen during IR construction.

.gfids$y contains a list of indirect calls for Control Flow Guard. This
wasn't working properly for ARM64EC: direct calls were being treated as
indirect calls. Make sure we correctly filter out direct calls.

This improves the protection from Control Flow Guard, and also fixes a
link error when using certain functions from oldnames.lib.

Replace it with a forward declaration instead. Analysis.h is pulled in
by all passes, but not all passes need to access the module.

startswith/endswith wrap starts_with/ends_with and will eventually go away (to more closely match string_view)

Add SwitchSection to return switchSection. The API will be removed soon.

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D121332

Identified with modernize-use-equals-default

Identified with readability-redundant-member-init.