Use dyn where possible, including dyn based progress traits

[Byron]

Implement a proper worktree reset, eventually leading to a high-level reset similar to how git supports it.

Facilitate compile time reduction

• upgrade to latest Prodash
• See if users of Progress can also use Count or dyn Count, or dyn Progress
• review all crates for unnecessary usage of generics
• split gix-pack data-io off using feature toggles
• Add gix feature toggles: remote-connection, blob-diff, describe, attributes->worktree-checkout, attribute->pathspecs->submodules, mailmap
• security: assure we don't read outside of the repository when refs are ../../../. Further, assure that we don't write such refs when receiving them from the server.

Tasks

• upgrade to
• worktree reset to match new index, with or without safety checks to prevent overwriting modified files or untracked files.
• figure out how this relates to the current checkout() method as technically that's a reset --hard with optional overwrite check. Could it be rolled into one, with pathspec support added?
• TBD

Postponed

What follows is important for resets, but won't be needed for cargo worktree resets.

• insert entry into index
• traverse tree with pathspec matching and insert entry into index.

Research

• How to integrate submodules
• How to deal with various modes like merge and keep? How to control refresh?
• Worthwhile to make explicit the difference between git reset and git checkout in terms of HEAD modifications. With the former changing HEADs referent, and the latter changing HEAD itself.