7036: Bump travis rubies r=hsbt a=deivid-rodriguez

### What was the end-user problem that led to this PR?

The problem was that hacks create confusion, even if they include TODO notes.

### What was your diagnosis of the problem?

My diagnosis was that we can should upgrade to the latest ruby releases to reduce the number of hacks we need to maintain.

### What is your fix for the problem, implemented in this PR?

My fix is to upgrade rubies and remove hacks.

### Why did you choose this fix out of the possible options?

I chose this fix because it's a good change.

Co-authored-by: David Rodríguez <deivid.rodriguez@riseup.net>

7059: Make `bundle clean` clean git extension directories r=hsbt a=dylanahsmith

Fixes #7058

This PR fixes it by adding the native extension directories for git gems to the ones for non-git gems.  This is used to get the unused extension directories (`stale_extension_dirs = extension_dirs - spec_extension_paths`) which was already excluding extension directories for git gems.

Co-authored-by: Dylan Thacker-Smith <dylan.smith@shopify.com>

7052: Introduce  `original_system`, `original_exec`, `unbundled_system`, and `unbundled_exec`  r=indirect a=deivid-rodriguez

### What was the end-user problem that led to this PR?

The problem was that the `clean_system` and `clean_exec` would print deprecation messages, but there was not alternative for them.

### What was your diagnosis of the problem?

My diagnosis was that the helpers are using deprecated behavior and that we should provide non deprecated alternatives.

### What is your fix for the problem, implemented in this PR?

My fix is to introduce `original_system`, `original_exec`, `unbundled_system`, and `unbundled_exec` for consistency with the rest of the helpers, and deprecate `clean_system` and `clean_exec`.

### Why did you choose this fix out of the possible options?

I chose this fix because while maybe not super pretty names, they offer an alternative consistent with the other helpers.


Co-authored-by: David Rodríguez <deivid.rodriguez@riseup.net>

To avoid activation of the `etc` gem.