Closes #48007 

Release Notes:

- Added editor setting for changing regex mode default in vim searches

Summary:

- Based on the report in #48007 and the discussion here
https://github.com/zed-industries/zed/pull/48127#issuecomment-3838678903
- There was feedback mentioning that vim-mode needs to default
vim-searches to use regex-mode (even when the editor regex-search
setting is disabled). However, it was suggested that a vim search
setting could be configured to adjust this behaviour.
- In this PR a new vim setting was added to change whether vim-searches
will use regex-mode by default, so now users can can configure
vim-search to not use regex-mode when typing the `/` character (or using
the vim search command).

Screen Captures:


https://github.com/user-attachments/assets/172669fb-ab78-41a1-9485-c973825543c5