Fix to support creating MRs for repositories cloned with SSH alias

[roveo]

PR Description

Use case: some repositories are cloned with a full SSH alias (without a user). E.g. in .ssh/config you have

Host gitlab
    HostName gitlab.com
    User git
    IdentityFile ...

and then you clone with git clone gitlab:foo/bar

According to the docs, you can add a service to config.yaml and it should work:

services:
  gitlab: 'gitlab:gitlab.com'

But currently it doesn't because lazygit expects all remote URLs to have a user. This can be fixed by the user by changing the URL to e.g. git@gitlab:foo/bar, but it breaks the user flow and is quite unexpected.

This PR changes defaultUrlRegexStrings and makes the user@ part of the remote URL optional. Fixes the issue for Github and Gitlab which use the default regexes.

Please check if the PR fulfills these requirements

• [*] Cheatsheets are up-to-date (run go generate ./...)
• [*] Code has been formatted (see here)
• [*] Tests have been added/updated (see here for the integration test guide)
• [*] Text is internationalised (see here)
• [*] If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• [*] Docs have been updated if necessary
• [*] You've read through your own file changes for silly mistakes etc

[roveo]

I think this fixes #5069

[stefanhaller]

Thanks, this looks good to me. (I'm not very familiar with this area of the code and functionality, so I hope I'm not missing something...)

I took the liberty of squashing your second commit into the first, I didn't see a reason why it should be a separate commit.

Also, next time please create a branch in your fork instead of using your master branch; this makes it slightly easier for me to work with it.