regcomp_invlist.c: Perl_populate_bitmap_from_invlist() optimize asserts

[bulk88]

Inside re.xs/re.dll, Perl_populate_bitmap_from_invlist() has half a dozen if(!invlist) _assert_libc() call sites. Atleast PERL_ARGS_ASSERT_POPULATE_BITMAP_FROM_INVLIST, invlist_iterinit(), invlist_iternext(), invlist_iterfinish() are all testing a C auto var that was proven inside PERL_ARGS_ASSERT_POPULATE_BITMAP_FROM_INVLIST to be true. "SV * invlist" is a C auto and I don't belive it is "reachable" under ISO C. Perl_populate_bitmap_from_invlist() never does & operator on it. But atleast MSVC 2022 is constantly re-reading this C auto. Also Perl_populate_bitmap_from_invlist() has only 1 call site, and MSVC hoisted/folded/inlined away "const Size_t len" since its always 8.

#define REGNODE_BBM_BITMAP_LEN /* 6 info bits requires 64 bits; 5 => 32 */ ((1 << (UTF_CONTINUATION_BYTE_INFO_BITS)) / CHARBITS)

since MSVC doesnt inline memcpy symbol func calls b/c WinPerl doesnt request it, make it obvious here to skip the libc call on all platforms.

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• This set of changes does not require a perldelta entry.