…ght yield identical stringsr #1183 (+1 squashed commits)

Squashed commits:

[e8e3387] Proposed fix for #1183 - creating multiple regex within short time might yield identical strings

Co-authored-by: Nikos Baxevanis <nikos.baxevanis@gmail.com>

Added a test to FixtureTests, to verify that #1183 is fixed as suggested here: #1187 (comment)

This required making sure that the outcome space of the regex pattern is great enough. Xeger seems to favor shorter strings, and this gave collisions when generating RegularExpressionValidatedType . So minimum length of the pattern in this type was lengthened from 1 to 20.

Removed assertion roulette in RegularExpressionGeneratorTests.CreateMultipleWithRegularExpressionRequestReturnsDifferentResults(...)
according to suggestion: #1187 (comment)

… now only shared on each thread.

…and with room for future perf improvement 😊