fusefs tests: handle -Wdeprecated* issues with GoogleTest 1.14.0

INSTANTIATE_TEST_CASE_P has been replaced with INSTANTIATE_TEST_SUITE_P.
Replace all uses of the former macro with the latter macro.

While here, address the fact that the latter macro doesn't permit some
of the constructions that the former macro did, e.g., empty parameters,
etc.

MFC after: 2 weeks
Reviewed by: asomers
Differential Revision: https://reviews.freebsd.org/D41398