This change prepares for allowing more flexible tag matching. For example, we may want to write "gpu" in a test and have it match both "cuda" and "rocm" devices, which we cannot do under the current API but can easily do under this design.
Replace uses of device_under_test() in a context that performs an equality test with a call to test_device_matches().
Replace uses of if_device_under_test() with test_device_matches() and delete if_device_under_test().
PiperOrigin-RevId: 568923117
Split the custom root and custom linear solve tests into separate test files.
Disable two slow custom linear solve tests.
Add a few jit decorators to slow tests in lax_control_flow_test.
PiperOrigin-RevId: 421901487