Specify/infer arguments for testing uninspectable signatures

[honno]

Should resolve #175 by re-introducing manual specification of arguments when testing uninspectable signatures.

Differences with pre-#110 test_signatures.py:

• Declarative approach to specifying manual arguments.
  • Arguments are explicitly specified for the functions/methods that use them, preventing assumptions leaking.
• Leverages inspect.Parameter.default to infer the majority of manual arguments.
• Tests all valid combinations of passing pos-or-kw arguments

[honno]

@asmeurer here are the current failures for array_api_compat.torch, which all look to be failing correctly. No function/method is being skipped now!

# dims (axes in torch) can't be a single int
array_api_tests/test_signatures.py::test_func_signature[permute_dims]
# no copy arg
array_api_tests/test_signatures.py::test_func_signature[reshape]
# shape is pos-only (should be pos-or-kw)
array_api_tests/test_signatures.py::test_func_signature[broadcast_to]
# no k arg (diagonal is used instead)
array_api_tests/test_signatures.py::test_func_signature[tril]
array_api_tests/test_signatures.py::test_func_signature[triu]
# methods don't exist
array_api_tests/test_signatures.py::test_array_method_signature[__array_namespace__]
array_api_tests/test_signatures.py::test_array_method_signature[to_device]
# not in linalg extension
array_api_tests/test_signatures.py::test_extension_func_signature[linalg.matrix_transpose]
array_api_tests/test_signatures.py::test_extension_func_signature[linalg.outer]
array_api_tests/test_signatures.py::test_extension_func_signature[linalg.tensordot]
array_api_tests/test_signatures.py::test_extension_func_signature[linalg.trace]

[honno]

This is nice to get in so merging.