test: make test_utxo_snapshots.sh use signet

[Sjors]

It currently requires recompiling, which doesn't seem necessary if we just use a lighter weight network like signet.

We could also drop this script entirely?

[Sjors]

cc @jamesob do you think it's still useful?

If so I'll look into switching it to Signet.

[maflcko]

I'd say for testing, the existing unit or functional test framework should be used. No objection for the bash script to exist, but I think longer term, it is clear that bash scripts won't be maintained in this repo, given that there are no reviewers for them and that the script is excluded from shellcheck completely (#27596 (comment)). Unit and functional test would at least run in the CI.

[fanquake]

Going to close this, given we should be removing the bash scripts in #29553.