In FTL world we store serialized FTL messages in Translation.string. When Search and Replace mass action is used, we should only replace values, not the entire string with the full FTL syntax.

Commit pushed to master at https://github.com/mozilla/pontoon https://github.com/mozilla/pontoon/commit/9bee538c9d76981bfab07c58b628516367677ef7 Fix bug 1393523: Search and replace text values only (#784) To make search and replace work for FTL strings, we can't just use Translation.string.replace(keyword, replacement) like for other file formats, becuse we store the entire source code of the FTL Message in Translation.string. Instead, we need to: 1. Parse each string and get AST 2. Recursively traverse AST and run find & replace on text values only 3. Serialize updated AST. This also fixes a that triggered Unsaved changes warning for FTL string when leaving the batch editor. We must hide batch editor first in order to display FTL editor properly.