boards: xtensa: Align testcase tags for intel_adsp boards

Aligns intel_adsp boards to be consistent about which testcase tags to
ignore or apply. This reduces the number of tests for intel_adsp_cavs15
because we now ignore networking and Bluetooth tests.  It increases the
number of tests for intel_adsp_cavs20 because we're no longer limited to
only kernel and sof tests.

intel_adsp_cavs18 and intel_adsp_cavs25 already had these tags and don't
need to be modified.

Signed-off-by: Maureen Helm <maureen.helm@intel.com>