Fix DateTime NewObject

[josesimoes]

Description

• Replace code creating new DateTime objects with standard and straightforward approach.

Motivation and Context

• The latest version of this code was using a much more convoluted approach (by calling generic NewObject()) instead of a simple approach considering this is a base type.
• Because the generic NewObject() was treating DateTime objects as value types, this could have implications regarding heap management.
• This was unveiled by tests and code analysis in the scope of Heap compaction is not working Home#1354.

How Has This Been Tested?

• Running GC stress tests.
  [run mscorlib tests]

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue with code or algorithm)
• New feature (non-breaking change which adds functionality to code)
• Breaking change (fix or feature that would cause existing functionality to change)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dev Containers (changes related with Dev Containers, has no impact on code or features)
• Dependencies (update dependencies and changes associated, has no impact on code or features)
• Documentation (changes or updates in the documentation, has no impact on code or features)

Checklist

• My code follows the code style of this project (only if there are changes in source code).
• My changes require an update to the documentation (there are changes that require the docs website to be updated).
• I have updated the documentation accordingly (the changes require an update on the docs in this repo).
• I have read the CONTRIBUTING document.
• I have tested everything locally and all new and existing tests passed (only if there are changes in source code).

[josesimoes]

Replaced with #2794