Add JGit binary check for plain text acceptance

[shanman190]

What's changed?

Use the same mechanism for plain text identification that Git utilizes.

What's your motivation?

To improve plain text identification. Retained the ability to explicitly use plainTextMasks as a first pass check, but it should no longer be necessary for most cases (UTF-16 encoded files can use plainTextMasks as an escape hatch as is typically done with .gitattributes).

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files