New rule S6588: Use `DateTime(Offset).UnixEpoch` instead of pointing to that date using the constructor

[mary-georgiou-sonarsource]

Implement new rule S6588: Use DateTime(Offset).UnixEpoch instead of pointing to that date using the constructor.

This rule should raise when a new DateTime, DateTimeOffset or DateOnly object is created with Date 1-1-1970.

• [ ] Implement Rule S6588 for C#
• [ ] Implement Rule S6588 for VB.NET

[csaba-sagi-sonarsource]

The rule should not cover DateOnly, because it does not have a UnixEpoch field that could be used instead.