Previously, the `_getconftestmodules` function was used both to load
conftest modules for a path (during `pytest_load_initial_conftests`),
and to retrieve conftest modules for a path (during hook dispatch and
for fetching `collect_ignore`). This made things muddy - it is usually
nicer to have clear separation between "command" and "query" functions,
when they occur in separate phases.
So split into "load" and "get".
Currently, `gethookproxy` still loads conftest itself. I hope to change
this in the future.