[TEST] Initialization errors are checked before returning "no tests to run" error

If there initialization errors and no tests to execute at the same time, better to return the initialization errors, whose check should be first then, as it might be that the "no tests to execute" is caused by the initialization errors.
Added tests for empty token chars on ngram tokenizer

This relates to #5120
[TEST] Added index templates tests for broken mapping and invalid settings scenarios
[TEST] Update testNGramCopyField to reflect the effect of an index_analyzer