[pyre] Add knob to control search paths

[dandanaila]

Scenario

We have a repo A for a python project. This has in its list of requirements another python repo B. In the current setup, the pyre linter is complaining for every import & every class imported from the module expose by B.

Current workaround

For the moment, the only way to get it working was to create a .pyre_configuration that included in its search_path: /opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages (that's where pip installed all the requirements). Given all the version numbers in the path, it's not really an ideal solution.

Possible solution

One idea would be having a knob dedicated to pyre, e.g., an environment variable similar to INPUTS_TARGET that would allow a user to specify a list of paths, that can be passed to the pyre binary (e.g., using --search-path for each element in the list when constructing the cmd).

Thanks!