sanitycheck: CONFIG_TEST_USERSPACE / userspace tag cleanup

- Delete CONFIG_TEST_USERSPACE=n no-ops because it's the default
since commit 7b1ee5cf

- Some tests have a "userspace" tag pretending to TEST_USERSPACE but
don't and vice versa: fix missing or spurious "userspace" tags in
testcase.yaml files.

Tests have a _spurious_ "userspace" tag when they PASS this command
cause none should pass:

  ./scripts/sanitycheck --tag=userspace -p qemu_x86 \
      --extra-args=CONFIG_TEST_USERSPACE=n  \
      --extra-args=CONFIG_USERSPACE=n | tee userspace.log

All tests run by this command must either fail to build or fail to run
with some userspace related error. Shortcut to look at all test
failures:

 zephyr_failure_logs() {
     awk '/see.*log/ {print $2}' "$@"
 }

Tests _missing_ "userspace" tag FAIL to either build or to run with some
userspace related error when running this:

  ./scripts/sanitycheck --exclude=userspace -p qemu_x86 \
      --extra-args=CONFIG_TEST_USERSPACE=n  \
      --extra-args=CONFIG_USERSPACE=n | tee excludeuserspace.log

Note the detection methods above are not 100% perfect because some
flexible tests like tests/kernel/queue/src/main.c evade them with #ifdef
CONFIG_USERSPACE smarts. Considering they never break, it is purely the
test author's decision to include or not such flexible tests in the
"userspace" subset.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>