Updates to IsEmailAddress and MustBeEmailAddress

[feO2x]

This pull request introduces significant enhancements to the email validation tests in the Light.GuardClauses library. The changes include adding new test data classes for valid and invalid email addresses, expanding the test coverage to include various span types, and refactoring existing tests to use the new test data classes.

Enhancements to email validation tests:

• Code/Light.GuardClauses.Tests/StringAssertions/InvalidEmailAddresses.cs: Added a new InvalidEmailAddresses class to provide test data for invalid email addresses and a subclass InvalidEmailAddressesWithNull to include null values.
• Code/Light.GuardClauses.Tests/StringAssertions/ValidEmailAddresses.cs: Added a new ValidEmailAddresses class to provide test data for valid email addresses.
• Code/Light.GuardClauses.Tests/StringAssertions/IsEmailAddressTests.cs: Added comprehensive tests for email validation using ReadOnlySpan, Span, Memory, and ReadOnlyMemory types, leveraging the new test data classes.
• Code/Light.GuardClauses.Tests/StringAssertions/MustBeEmailAddressTests.cs: Refactored existing tests to use the new ValidEmailAddresses and InvalidEmailAddresses classes, and added tests for ReadOnlySpan, Span, Memory, and ReadOnlyMemory types. [1] [2] [3] [4]

Codebase improvements:

• Code/Light.GuardClauses.Tests/ExecuteReadOnlySpanAssertion.cs: Introduced new delegate types to handle assertions for ReadOnlySpan and Span types, enhancing code readability and maintainability.

These changes collectively improve the robustness and coverage of the email validation functionality in the Light.GuardClauses library.