Remove @inbounds in tuple iteration (#48297)
* Remove @inbounds in tuple iteration
LLVM can prove this inbounds and the annotation weakens the
inferable effects for tuple iteration, which has a surprisingly
large inference performance and precision impact.
Unfortunately, my previous changes to :inbounds tainting weren't
quite strong enough yet, because `getfield` was still tainting
consistency on unknown boundscheck arguments. To fix that, we
pass through the fargs into the fetfield effects to check if
we're getting a literal `:boundscheck`, in which case the
`:noinbounds` consistency-tainting logic I added in #48246
is sufficient to not require additional consistency tainting.
Also add a test for both effects and codegen to make sure this doens't regress.
* Int64 -> Int
* fixup typo
