Ensure that all non-static symbols are guarded by MLD_CONFIG_{INTERNAL/EXTERNAL}_API_QUALIFIER

[hanno-becker]

Reported by @flynd in #934

Acceptance criteria:

• Manual check confirms that with MLD_CONFIG_INTERNAL_API_QUALIFIER and MLD_CONFIG_EXTERNAL_API_QUALIFIER set to static, no symbols of external linkage are generated.

[flynd]

I have confirmed that the change in #951 fixes all the functions that I currently have patched locally to static to allow building as a single unit.
However there are several data tables which should also be declared static in aarch64_zetas.c, poly_unpack_table.c, rej_uniform_eta_table.c, rej_uniform_table.c, and their declarations in arith_native_aarch64.h.

[hanno-becker]

I believe this is fixed with #1043.