[AIX] Support per global code model. (#79202)
Exploit the per global code model attribute on AIX. On AIX we need to
update both the code sequence used to access the global (either 1 or 2
instructions for small and large code model respectively) and the
storage mapping class that we emit the toc entry.
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Co-authored-by: Amy Kwan <akwan0907@gmail.com>
