Bring one group board to CE

This is a backport of one group issue boards from EE, most of the files have been backported and some required minor changes.

Things to double check:

Try to spot any unnecessary changes

Known issues

These issues are also reproduced in master(EE and CE) so they are not related to this MR:

• Javascript error when accessing group

TypeError: Cannot read property 'hasAttribute' of null
    at At.data (boards_bundle.js:261)
    at At.<anonymous> (vue.esm.js:1161)
    at Ke (vue.esm.js:3386)
    at Ve (vue.esm.js:3345)
    at We (vue.esm.js:3284)
    at At.e._init (vue.esm.js:4558)
    at new At (vue.esm.js:4659)
    at HTMLDocument.<anonymous> (boards_bundle.js:252)
    at l (jquery.js:3187)
    at Object.fireWith [as resolveWith] (jquery.js:3317)
    at ready (jquery.js:3536)
e.(anonymous function) @ console.js:32
oe @ vue.esm.js:1717 

• Add issues modal is not showing for groups on CE and EE

TODO

• Add documentation
• Javascript cleanup(it generated some unecessary changes when backported)

EE counterpart: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4606

closes #38337 (closed)