Documentation: kunit: Document new parameterized test features

Documentation: kunit: Document new parameterized test features

This patch updates the KUnit docs to show how to use the new
parameterized test context to share resources between parameter runs.
It documents and show examples of different ways the test user can
pass parameter arrays to a parameterized test. Finally, it specifies the
parameterized testing terminology.

Link: https://lore.kernel.org/r/20250826091341.1427123-8-davidgow@google.com
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Marie Zhussupova <marievic@google.com>
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>