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/Cargo.lock

@@ -2400,6 +2400,12 @@ dependencies = [
  "zstd",
 ]
 
+[[package]]
+name = "nohash-hasher"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2bf50223579dc7cdcfb3bfcacf7069ff68243f8c363f62ffa99cf000a6b9c451"
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -4907,6 +4913,7 @@ dependencies = [
  "lexical-core",
  "md-5",
  "mimalloc",
+ "nohash-hasher",
  "os_str_bytes",
  "path-clean",
  "pretty_assertions",