Use the new feature of Go 1.24, fix linter warnings.
This change was produced by:
- running golangci-lint run --fix
- sed 's/context.Background/t.Context/' -i `git grep -l context.Background | grep test.go`
- manually fixing broken tests
- itest, lntest: use ht.Context() where ht or hn is available
- in HarnessNode.Stop() we keep using context.Background(), because it is
called from a cleanup handler in which t.Context() is canceled already.
we make the index assertion db independant so it is a noop for
a future native sql backend. This allows us to reuse even more
tests for the different db architectures.
This commit starts reusing test cases which are not dependant on
the kv db backend. So they can be later used with the native db
implementation as well.
This commit moves most of the code into its own package. It is
the smallest code move possible without moving import cycles and
keeping the changes to the code base as small as possible during
refactor.
