Implemented an internal getrandom to avoid calls to the public one in
table.h

---------

Co-authored-by: Sriya Pratipati <sriyap@google.com>

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.

This patch implements `hcreate(_r)/hsearch(_r)/hdestroy(_r)` as
specified in https://man7.org/linux/man-pages/man3/hsearch.3.html.

Notice that `neon/asimd` extension is not yet added in this patch. 

- The implementation is largely simplified from rust's
[`hashbrown`](https://github.com/rust-lang/hashbrown/blob/master/src/raw/mod.rs)
as we only consider fix-sized insertion-only hashtables. Technical
details are provided in code comments.

- This patch also contains a portable string hash function, which is
derived from [`aHash`](https://github.com/tkaitchuck/aHash)'s fallback
routine. Not using any SIMD acceleration, it has a good enough quality
(passing all SMHasher tests) and is not too bad in speed.

- Some general functionalities are added, such as `memory_size`,
`offset_to`(alignment), `next_power_of_two`, `is_power_of_two`.
`ctz/clz` are extended to support shorter integers.