[FW][MOV] calendar: "Calendar" app from "Misc" to "Productivity"

[fw-bot]

To improve the structure of the documentation, the "Miscellaneous" section should be limited as much as possible.

This commit:

• renames "Calendars" into "Calendar" (as the app name)
• moves the app from the "Miscellaneous" section to the "Productivity" section
• fixes the wrong file structure to follow the toc (e.g. general/calendars/outlook/outlook_calendar -> productivity/calendar/outlook)

task-3217827

Forward-Port-Of: #4109
Forward-Port-Of: #4032

[robodoo]

Pull request status dashboard.

[fw-bot]

@jcs-odoo cherrypicking of pull request #4032 failed.

stdout:

Auto-merging content/applications/general.rst
Auto-merging content/applications/productivity.rst
CONFLICT (content): Merge conflict in content/applications/productivity.rst

stderr:

22:36:59.920201 git.c:455               trace: built-in: git cherry-pick 2de686da3a6fa3e5afd5fe0a9acf5817ea9d8771
error: could not apply 2de686da3... [MOV] calendar: "Calendar" app from "Misc" to "Productivity"
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
----------
status:

Either perform the forward-port manually (and push to this branch, proceeding as usual) or close this PR (maybe?).

In the former case, you may want to edit this PR message as well.

[jcs-odoo]

@robodoo r+