Greatly improve terminal features! Persistent terminals

[G-Rowell]

Hi all,

(terms = NeoVim :terminals)

This is a PR to greatly improve our term functionality.
This can be summarised as now having persistent terms!
I particularly aim to never leave NeoVim when working, so this helps a lot in that sense!

Improvements:

• Persistent terms with
  -- These can create as many terms as you wish (as they just generate a new term)
  -- <leader> + w for a window term
  -- <leader> + v for a vertical split term
  -- <leader> + h for a horizontal split term
  -- A newly created term will start in insert mode

• Escape term mode with jk

• Escape & hide term with JK

• Bring them back with a Telescope picker terms
  -- <leader> + W (note, capital W, so technically <leader> + <shift> + w
  -- This runs :Telescope terms

• Improved close buffer behavior generally (also enables hiding of terms to keep them persistent)

• this also removes the ToggleTerm plugin, so you should run :PackerSync

Known issues / wishlist:

• Auto start in insert mode when recovering one with the picker
• Statusline appears in terms again, need to fix this
• Improve picker for 100 columns terminal windows like I run (can't see the term buffer)
• Recovering window terms doesn't always put it back on the bufferline, if you are in a split of a term it will go into that window

Tl;dr monkey can type cmatrix in terms now!

[G-Rowell]

Don't merge until I give the okay, I may be working on fixes

[G-Rowell]

Tested & approved by @siduck76

[siduck]

waiting for @Akianonymus 's review and test!