feat(tvix/eval): Put interner in a thread-local RefCell HEAD r/8455 canon

Rather than making the interner be a global lazy_static mutex, put it in
a thread-local RefCell. This doesn't change anything in terms of
sharing (since we're currently actually just single threaded), but
avoids the overhead of a mutex, for a nice performance boost (compared
to the mutex version):

hello outpath           time:   [726.71 ms 729.79 ms 735.69 ms]
                        change: [-5.7277% -3.9733% -2.1144%] (p = 0.00 < 0.05)
                        Performance has improved.

Change-Id: I240b238dcbaf854ebafc3017b4425fb7d7b91b03
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12048
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: aspen <root@gws.fyi>

0 files changed, 0 insertions, 0 deletions