twister: harness: recording: Allow multiple patterns

Extend Twister Harness 'recording' feature to allow multiple
regular expression patterns to extract different types of records
from test output.

Add 'merge' recording mode to collect all extracted data fields
into a single record object of the test instance.

Export to CSV file now takes all field names occurred in the collected
records, sort it alphabetically, and then use it for columns instead of
using only the first record's fields. This is done to address possible
situation when records have different set of fields.

Adjust Twister documentation and test suite to the above changes.

Signed-off-by: Dmitrii Golovanov <dmitrii.golovanov@intel.com>