Make SuperILC to execute .cmd/.sh only (dotnet/coreclr#27854)

Make SuperILC to execute .cmd/.sh only (dotnet/coreclr#27854)

Until now, SuperILC was executing both .cmd/.sh files of tests and .exe
files it has found in the test folders that didn't match the .cmd/.sh
file names. This is different from how coreclr tests are run in regular
test runs. Only the .cmd/.sh files should be executed, the .exe files
with names not matching the .cmd/.sh files are always just helper
applications used by the tests and not the main test executables.
This change updates SuperILC to execute only the .cmd / .sh, thus
getting rid of about 5 failures from the coreclr pri 1 test runs.

Commit migrated from https://github.com/dotnet/coreclr/commit/76751786c52895a96dac39e83570d14bb2b42b49