Fix misalignment between AdvancedSettings defaults and VCRHandler constructor

[Greybird]

Description

When VCRHandler is created with a null AdvancedSettings, or an AdvancedSettings with a null MatchRules property, then the handler _matchRules is set to a new instance of MatchRules.
However, when AdvancedSettings is instanciated, it uses MatchRules.Default by default for its MatchRules property.
As passing no AdvancedSettings is expected to behave exactly like passing a default AdvancedSettings instance, this creates a bug, where if no AdvancedSettings is provided, all requests are matching by default.

Testing

1 Unit tests has been updated, and another has been created to confirm the bug and the fix.

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)

[nwithan8]

Great catch! Approved.