update parser to handle Specta 0.2.1

Specta 0.2.1 introduced indentation in the test output.

This commit updates the regexes for:

* FAILING_TEST_MATCHER
* TESTS_RUN_COMPLETION_MATCHER
* TESTS_RUN_START_MATCHER
* TEST_SUITE_START_MATCHER
* EXECUTED_MATCHER
* SAMPLE_SPECTA_TEST

To allow for optional whitespace at the start of the lines