When using the Web IDE

One exception: there is an existing MR for the current branch and the
branch is non-default and non-protected.

Extended mock_data for ide/stores to have different types of branches:
default, protected and regular

Cleaned new MR checkbox view

- Pull the new MR option out into it's own component
- Default MR checkbox to true when creating a new MR and committing to a
  branch that does not have an MR
- Still change the MR checkbox to false when a user is on a branch that
  already has an MR
- Hide MR option when on a branch that already has an MR and committing
  to current branch
- Don't default to true when committing directly to master

Before the user had to choose between committing to a new branch,
committing to a new branch AND creating an MR, or committing to the
current branch regardless of whether or not it already has an MR.

This commit separates the creation of an MR from whether or not they
commit to an existing or new branch

#2691

Closes #45698

fixed form collapsing too soon

remove object.assign instead directly assign to state
created new constants

reduced duplicated CSS

remove close button in tab
fix height not working in form
restored stage & unstage all changes
disable merge request radio button when staged & unstaged changes exist

Improves the web IDE commit message imput by highlighting any characters
on the first line after 50 & every other line after 72

Closes #44832

This also makes the IDE generally available