Consider configuration changes to aid in testing with `--pyargs`

[braingram]

Some packages (like sunpy) run most of their CI with --pyargs where the tests can have unpredictable paths (note these are not schema tests because I think this issue is leading them to not test their schemas with this plugin):

 [gw3] [  0%] PASSED ..\..\.tox\py312\Lib\site-packages\sunpy\image\tests\test_resample.py::test_reshape 
..\..\.tox\py312\Lib\site-packages\sunpy\image\tests\test_transform.py::test_rotation[90.0-1] 
[gw2] [  0%] PASSED ..\..\.tox\py312\Lib\site-packages\sunpy\coordinates\tests\test_transformations.py::test_hci_hci 
..\..\.tox\py312\Lib\site-packages\sunpy\coordinates\tests\test_transformations.py::test_hme_gei_sunspice 

Note the including of .tox\py312\Lib. This does not place nice with the asdf_schema_root:

pytest-asdf-plugin/src/pytest_asdf_plugin/plugin.py

Line 18 in 2e52e73

parser.addini("asdf_schema_root", "Root path indicating where schemas are stored")

One possibility is to change (or augment) the current path-based configuration to something uri based. Something like asdf_schema_uri_pattern with perhaps a uri pattern (supporting wildcards) that pytest-asdf-plugin will use to find schemas to test.

Pros:

• compatible with --pyargs and non-pyargs runs
• the plugin can check if the id matches the registered uri (which isn't guaranteed and is often tested separately)

Cons:

• requires schemas to be registered with asdf (which I think is the case for all packages)
• will miss bugs in schema registration where if a schema isn't registered it will be silently ignored (there is not anything that currently checks this so it's not a new issue)