Change `ModulePass::skipModule` to take const Module reference.
Additionally, make `OptPassGate::shouldRunPass` const as well as for
most implementations it's a const query. For `OptBisect`, make
`LastBisectNum` mutable so it could be updated in `shouldRunPass`.

Additional minor cleanup: Change all StringRef arguments to simple
StringRef (no const or reference), change `OptBisect::Disabled` to
constexpr.

- Do not call pass initialization from pass constructors.
- Instead, pass initialization should happen in the `initializeAnalysis`
function.
- https://github.com/llvm/llvm-project/issues/111767

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

Namespaces are terminated with a closing comment in the majority of the
codebase so do the same here for consistency. Also format code within
some namespaces to make clang-format happy.

C++20 comes with std::erase to erase a value from std::vector.  This
patch renames llvm::erase_value to llvm::erase for consistency with
C++20.

We could make llvm::erase more similar to std::erase by having it
return the number of elements removed, but I'm not doing that for now
because nobody seems to care about that in our code base.

Since there are only 50 occurrences of erase_value in our code base,
this patch replaces all of them with llvm::erase and deprecates
llvm::erase_value.

Differential Revision: https://reviews.llvm.org/D137149

Move structural hashing into virtual methods on Pass. This will
allow MachineFunctionPass to override the method to add hashing of
the MachineFunction.

Differential Revision: https://reviews.llvm.org/D120123

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

Number of lines output by preprocessor:
before: 1065940348
after:  1065307662

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D120659