chore(3p/sources): Bump channels & overlays

- Adjust to ecl 23.9.9 release

- Regenerate go protos after protoc-gen-go update

- Drop dhall fork which hasn't kept up with 1.42.*

- Address new clippy warnings:

  - Variant naming of Error::ValidationError
  - Simplify .try_into().unwrap()
  - Drop unnecessary identity function
  - Test module must be last in file
  - Drop unused `pub use`

- Update agenix to 0.15.0. Current master has a installCheckPhase that
  doesn't work with C++ Nix 2.3.*:
  a23aa271be (commitcomment-137185861)

Change-Id: Ic29eef20d6fd1362ce1031364a5ca6b4edf195bd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10615
Reviewed-by: aspen <root@gws.fyi>
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>

tvix/castore/src/proto/tests/directory.rs

@@ -141,9 +141,7 @@ fn digest() {
 
     assert_eq!(
         d.digest(),
-        (&hex!("af1349b9f5f9a1a6a0404dea36dcc9499bcb25c9adc112b7cc9a93cae41f3262"))
-            .try_into()
-            .unwrap()
+        (&hex!("af1349b9f5f9a1a6a0404dea36dcc9499bcb25c9adc112b7cc9a93cae41f3262")).into()
     )
 }