Also shuts down `Broker`, which, before this PR, we did start in
`start()` but relied on the fixture to stop. Do it a bit earlier so
that, after `NeonEnv.stop()` returns, there are no child processes using
`repo_dir`.
Also, drive-by-fixes inverted logic around `ps_assert_metric_no_errors`,
missed during https://github.com/neondatabase/neon/pull/6295
---------
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
neon_fixtures.py has grown to unmanageable size. It attracts conflicts.
When adding specific utils under for example `fixtures/pageserver`
things sometimes need to import stuff from `neon_fixtures.py` which
creates circular import. This is usually only needed for type
annotations, so `typing.TYPE_CHECKING` flag can mask the issue.
Nevertheless I believe that splitting neon_fixtures.py into smaller
parts is a better approach.
Currently the PR contains small things, but I plan to continue and move
NeonEnv to its own `fixtures.env` module. To keep the diff small I think
this PR can already be merged to cause less conflicts.
UPD: it looks like currently its not really possible to fully avoid
usage of `typing.TYPE_CHECKING`, because some components directly depend
on each other. I e Env -> Cli -> Env cycle. But its still worth it to
avoid it in as many places as possible. And decreasing neon_fixture's
size still makes sense.
