Fix several, relatively new, issues.

Fixes:

• Check if any value is altered before attempting to run an alter statement for the dynamic table
• Suppress whitespace diff for query parameter in the dynamic table resource
• Leverage in schema syntax for dynamic table ShowByID method
• Compute skip_header parameter correctly in the file format resource
• Check if any value is altered before attempting to run an alter statement for the file format

There is one more problem with file format resource: altering the comment. It was mistakenly removed in the change #1917, but also a new change #2163 messes with AlterFileFormatOptions which requires a bit more of work.

Fixes #1947, fixes #2134, fixes #2173, fixes #2176.