Add update validations to SnippetInputAction

What does this MR do?

This MR adds some specific validation in the SnippetInputAction class when the action is an update operation.

An update operation can only update the content not renaming. A move operation instead, can rename the file and update the content.

Refs #219474 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content