[NEOS-1581] Update tests to use slogt

[nickzelei]

found this package that bridges the *testing.T logger with slog.Logger

Would be great to use this in our tests and replace our current use of discardLogger

https://github.com/neilotoole/slogt

That package is pretty small, it may make sense to just move this into internal/slogt instead of adding as an external dependency.

_{From SyncLinear.com | NEOS-1581}

[nickzelei]

@alisha.kawaguchi has done some work here to get this setup, now we just need to apply it everywhere: https://github.com/nucleuscloud/neosync/blob/main/internal/testutil/utils.go#L22