Fix getting DateTime value from boxed object

[josesimoes]

Description

• Add return value to Expand.
• Improve code in GetDateTimePart___I4__SystemDateT to deal with fail/success of call to Expand.
• Add code to GetValuePtr to process boxed DateTime objects.

Motivation and Context

• Trying to get a pointer to a boxed DateTime object was not possible.
• Failing to expand a DateTime wasn't being properly handled. It just continued happily with whatever rubbish was in the memory.

How Has This Been Tested?

Using the following code:

var now = DateTime.UtcNow;
var nowString = now.ToString();

Console.WriteLine("OUTPUT_1: " + nowString);
Console.WriteLine($"OUTPUT_2: {now}");

Notes:

1. the 1st call outputs the already built string)
2. the 2nd call is processed by Roslyn which adds a call to String.Format inside of which the output argument is boxed inside an array.

Output before the fix:

OUTPUT_1: 01/01/1980 03:35:58
OUTPUT_2: 53375/00/59512 60928:53375:01

Output after the fix:

OUTPUT_1: 01/01/1980 03:40:08
OUTPUT_2: 01/01/1980 03:40:08

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: josesimoes [email protected]

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