feat(tvix/eval): Store hash in key of interner

Rather than storing the leaked allocation for the string as the key in
the interner, store the hash (using NoHashHashBuilder). I thought this
would improve performance, but it doesn't:

hello outpath           time:   [736.85 ms 748.42 ms 760.42 ms]
                        change: [-2.0754% +0.4798% +2.7096%] (p = 0.72 > 0.05)
                        No change in performance detected.

but it at least doesn't *hurt* performance, and it *does* avoid an
`unsafe`, so it's probably net good.

Change-Id: Ie413955bdb6f04b1f468f511e5ebce56e329fa37
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12049
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: aspen <root@gws.fyi>

tvix/eval/Cargo.toml

@@ -35,6 +35,7 @@ sha1 = "0.10.6"
 md-5 = "0.10.6"
 data-encoding = "2.6.0"
 rustc-hash = "2.0.0"
+nohash-hasher = "0.2.0"
 
 [dev-dependencies]
 criterion = "0.5"