Reverts llvm/llvm-project#152748

This is a follow up to the RFC here:

https://discourse.llvm.org/t/rfc-implementation-of-stdio-on-baremetal/86944

This provides the stdout/stderr/stdin symbols (which now don't have to
provided by the user). This allows the user to have access to all
functions, currently I've only tested `fprintf` but in theory everything
that works in the generic folder should work in the baremetal
configuration.

All streams are _non-buffered_, which does NOT require flushing. It is
based on the CookieFile that already existed

This is the first step in preparation for:
https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450

This patch fixes:

randomness.h and getauxval.cpp were passing ssize_t as size_t
kernel_statx.h was assigning an uint64_t to uintptr_t
fopencookie.cpp was trying to create a FileIOResult using ssize_t but the constructor expected a size_t
thread.h was trying to call free_stack (which takes a size_t) with an unsigned long long. free_stack does the calculations using uintptr_t, so I changed the passing values to size_t

This is a part of #97655.

Reverts llvm/llvm-project#98075

bots are broken

This is a part of #97655.

reland of https://github.com/llvm/llvm-project/pull/98215

Additionally adds proxy headers for FILE and the fopencookie types

The arm32 build has been failing due to redefinitions of the off_t type.
This patch fixes this by moving off_t to a proper proxy header. To do
this, it also moves stdio macros to a proxy header to hopefully avoid
including this proxy header alongside this public stdio.h.

Reverts llvm/llvm-project#98215

Breaks linux bots

The arm32 build has been failing due to redefinitions of the off_t type.
This patch fixes this by moving off_t to a proper proxy header. To do
this, it also moves stdio macros to a proxy header to hopefully avoid
including this proxy header alongside this public stdio.h.