[Lazygit] Filter branches using expressions

### Is your feature request related to a problem? Please describe. Quite often, developers create branches with similar names, or at least using keywords that could be a common branch name. For example, people may create branches like `revert-xxx-from-main`, `improvements-main-workflow`, `dev-test`, `username/dev-improvements`, `username/dev-integration`, `user/featurex/dev` etc. When looking for a common branch like `main` or `dev`, we have to scroll a lot to find the correct branch for an operation in the branches panel. I think a similar issue may apply to Commits panel as well, but personally I don't need to search with reg exp in that panel often. ### Describe the solution you'd like Searching/filtering using `/` could use regular expressions to search/filter. We could then use something like `^main` or `^main$` to search for the exact branch. ### Describe alternatives you've considered Using terminal instead of lazygit and use auto-complete with commands.