DEV: Switch our fast_xor gem for xorcist (PR #10565)

We use the xor function as part of password hashing and we want to use a faster version than the native ruby xor’ing feature so we use a gem for this.

fast_xor has been abandoned, and xorcist fixed our initial holdup for switching in

xorcist also has jruby support so we can remove our jruby fallback logic.

Didn’t add any new tests here because we already have existing tests that should catch any issues.