Checking out non-local branches in telescope picker

[tvsfx]

It's currently hard to use the telescope worktree creation functionality, because it only works well for branches that have been checked out locally as well. There are a few issues when trying to create a worktree from a tracking branch:

1. The Git.has_branch logic will not find the branch (the git branch list does not contain remote tracking branches) and hence a new branch will incorrectly be created here. Fix: check for remote tracking branches as well
2. The following issue in git-worktree v1 still applies when one tries to create a git worktree from a remote-tracking branch: https://github.com/ThePrimeagen/git-worktree.nvim/issues/77. To summarize, for the new branch the <remote>/ prefix is kept in the local branch name as well, which results in a rather confusing user experience (e.g. in git log, there's now two references called <origin>/<branch>). Potential fix (related PR: https://github.com/polarmutex/git-worktree.nvim/pull/20.): git checkout and git worktree add have the same semantics, where if the starting branch is a tracking branch that does not exist locally and is present in a single remote, then a local checkout is created. Therefore, the Telescope git_branches command has faced a similar concern already, where remote branches are shown but usually what the user wants is to checkout a new, local branch (relevant issue: https://github.com/nvim-telescope/telescope.nvim/issues/1932). They have solved this by binding the function git_track_branch (https://github.com/nvim-telescope/telescope.nvim/blob/5972437de807c3bc101565175da66a1aa4f8707a/lua/telescope/actions/init.lua#L748-L756) to \<C-T>, allowing one to pass the --track option to git checkout, which provides the correct semantics. The telescope picker for git-worktree could similarly allow passing the --track option to git worktree add.
3. [Not related to telescope] I'm also not quite sure why fetching and setting the upstream here https://github.com/polarmutex/git-worktree.nvim/blob/500629d0ad916ec362f53ecf21f84f3ba445f73e/lua/git-worktree/worktree.lua#L112C1-L117C1 is necessary in the default case. This seems to differ from the git-worktree semantics one would expect, and seems to cause the "double origin" part of the aforementioned issue (https://github.com/ThePrimeagen/git-worktree.nvim/issues/77).

[rbmarliere]

@tvsfx Please give a shot at #32 ! Thank you.