Add regex tests for openconfig-yang-types.yang

[wenovus]

Tests for both posix-pattern and XSD patterns all pass on https://github.com/openconfig/models/pull/920.

NOTE: Failures are expected in the demo runs on openconfig/public since the patterns themselves are being changed/fixed.

Demo openconfig/public output on posix-pattern (this table will be automatically posted for both posix-pattern and pattern once #11 is merged:

leaf	typedef	error
date-and-time	date-and-time	0000-01-01T00:00:00Z did not match
date-and-time	date-and-time	9999-12-31T23:59:59Z did not match
date-and-time	date-and-time	1985-04-12T23:20:50.52Z did not match
date-and-time	date-and-time	2001-04-12T23:20:50.42424242Z did not match
date-and-time	date-and-time	1996-12-19T16:39:57-08:00 did not match
date-and-time	date-and-time	2006-12-20T00:39:57Z did not match
date-and-time	date-and-time	1937-01-01T12:00:27.87+00:20 did not match
date-and-time	date-and-time	0000-01-01T00:00:00+00:00 did not match
date-and-time	date-and-time	0000-01-01T00:00:00-00:00 did not match
date-and-time	date-and-time	1990-12-31T23:59:60Z did not match
date-and-time	date-and-time	1990-12-31T15:59:60-08:00 did not match
date	date	0000-00-01 matched but shouldn't
date	date	0000-01-00 matched but shouldn't
date	date	0000-13-01 matched but shouldn't
date	date	0000-20-01 matched but shouldn't
date	date	0000-33-01 matched but shouldn't
date	date	0000-01-32 matched but shouldn't
date	date	0000-01-40 matched but shouldn't

All XSD tests fail since the tests currently have anchors.