Selection of individual strings for bulk edit

### Describe the problem

The bulk edit feature allows to perform a search and apply an action to all strings returned from that search. However, the search seems to allow to filter only based on one characteristic and there is no way to for example apply labels to a fine-grained selection of strings.
Not sure if custom search would work, but if it would the search would have to be quite long/detailed anyway to catch the relevant ones.

### Describe the solution you'd like

In addition to 'search & apply', it would be helpful to have a way to select individual strings to which the bulk action would be applied. A simple checkbox for each string would allow to make this selection. I hate to make the reference because the tool really isn't that good, but it could look/work similar as in Transifex:

### Describe alternatives you've considered

* The live preview as described in #4106 would already help a bit but still would not allow for a fine-grained & visual selection of strings. Maybe this request (selection of individual strings) could be an enhancement on top of [#4106](https://github.com/WeblateOrg/weblate/issues/4106).
* _Combining_ this manual selection with a filter would be nice to help narrow down the list of strings one would have to look at, so that's a nice addition. But I also understand that that could potentially make it more tricky, 'cause what would happen if you select a string via the checkbox and then change the search that makes the selected string invisible...

### Screenshots

_No response_

### Additional context

_No response_