Add boundscheck in bindingkey_eq to avoid OOB access due to data race (#54671)
The race here is that svec might be replaced and a new binding
introduced into the keyset while we hold a reference to the old svec,
which led to a OOB access on the svec with the index a binding
introduced at the same time. This now introduces a bounds check which
will force taking the lock if we fail the lookup i.e we had a data race.
Fixes https://github.com/JuliaLang/julia/issues/54285
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Co-authored-by: Jameson Nash <vtjnash@gmail.com>