Fix #10785 Review of footer plugin

[allyoucanmap]

Description

This PR introduces changes to the footer plugin:

• reviewed configuration
• included support for a fixed menu at the bottom of the page
• the footer plugin has been included in all pages including viewer (only the menu items will be visible)
• removed old Footer plugin to avoid confusion
• refactor the menu component removing unused props and logic
• show about, documentation and github links in the footer plugin

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Minor changes to existing features

Issue

What is the current behavior?

#10785

What is the new behavior?

Refactor of the footer plugin including it in all pages

Breaking change

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes, and I documented them in migration notes

Other useful information

[offtherailz]

LGTM, only 2 notes:

• Map now contains 2 footers (mobile none). Not sure if it make sense to have a footer fixed on map view only for 3 items (maybe less), like about etc...
• I see there is the possibility to keep an html footer. It will be still sticked to the bottom of the browser ? Some client may need long footer notes. In this case how we can manage them
  You can clarify these things at project level and merge after that.

[tdipisa]

@allyoucanmap please remove the new footer from resource pages only for now (maintain it on admin pages). Let's maintain it fixed as you are proposing.