Bulk operations and search and replace

**Is your feature request related to a problem? Please describe.**
Right now, "Search and replace" and "Bulk edit" are distinct functions, while they serve almost same purpose, what can be confusing for users.

**Describe the solution you'd like**

* Extend "Bulk edit" to support text replacements as well.
* This would cover https://github.com/WeblateOrg/weblate/issues/4022 as all search capabilities would be available there
* The question is what to do with the preview. Is https://github.com/WeblateOrg/weblate/issues/4106 good enough replacement?

**Describe alternatives you've considered**
Alternative approach might be to add search field to the "Search and replace".