More config v6 tests

[adams85]

Describe the purpose of your pull request

Adds a few additional test cases for testing config v6 features.

Also, fixes a few edge cases where user attribute values was not converted to their canonical string representations.

Requirement checklist (only if applicable)

• I have covered the applied changes with automated tests.
• I have executed the full automated test set against my changes.
• I have validated my changes against all supported platform versions.
• I have read and accepted the contribution agreement.

[adams85]

ConfigCat.Client.Benchmarks.MatrixTestBenchmark (LogInfo = False)

Diff	Method	Mean	Error	Allocated
Old	MatrixTests_ConfigV6	17.61 ms	0.504 ms	13.84 MB
New		15.71 ms (-11%)	0.469 ms	11.75 MB (-15%)

[sonarcloud]

Quality Gate passed

Issues
5 New issues

Measures
0 Security Hotspots
94.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud