Avoids the really sloppy flag passing to `open_pikerd()` and allows for
separation of the individual docker daemon starts.
Also add a new `root_conf() -> Path` fixture which will open and load
the `dict` for the new root `conf.toml` file.
Since `.config.load()` was changed to not touch conf files by default
(without explicitly setting `touch_if_dne: bool`), this ensures both the
global module value is set and the `brokers.toml` file exists before
every test.
Not sure how this worked before but we need to also override the
`piker._config_dir: Path` in the root actor when running in `pytest`; my
guess is something in the old test suite was masking this problem after
the change to passing the dir path down through the runtime vars via
`tractor`?
Also this drops the ems related fixtures/factories since they're
specific enough to define in the clearing engine tests directly.
Questrade is the default broker backend (for now) so the CI
can run using a practice account token handed down through an
env variable. If we add a cached directory to the build then the token
should remain persistent in the brokers config and will only need to be
updated if something goes wrong.
Also, add a `--confdir` flag for pytest much in the same way as for
the `piker` cli.