tests/tcg: reduce the number of plugin tests combinations

tests/tcg: reduce the number of plugin tests combinations

As our set of multiarch tests has grown the practice of running every
plugin with every test is becoming unsustainable. If we switch to
ensuring every test gets run with at least one plugin we can speed
things up.

Some plugins do need to be run with specific tests (for example the
memory instrumentation test). We can handle this by manually adding
them to EXTRA_RUNS. We also need to wrap rules in a CONFIG_PLUGIN test
so we don't enable the runs when plugins are not enabled.

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250725154517.3523095-12-alex.bennee@linaro.org>