Port dotnet feature: .Net: Rename IsFilterable to IsIndexed and IsFullTextSearchable to IsFullTextIndexed

[github-actions]

Original issue

#11441

Description

Motivation and Context

#11130

Description

Rename IsFilterable to IsIndexed and IsFullTextSearchable to IsFullTextIndexed

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

\n Relates to #11441