qt: Add Window menu

Summary:
Overall this PR does the following:

• add top level menu Window
• add Minimize and Zoom actions to Window menu
• move Sending/Receiving address to Window
• remove Help->Debug menu and add one menu entry for each debug window tab in the Window menu

The ellipsis in the name of Sending/Receiving addresses actions are be removed, according to common practices (https://stackoverflow.com/a/637708).
Ellipsis at the end of the name of menu actions suggest that user input is expected.

Backport of Core PR14573 and PR16514

PR16514 removes the RPCConsole::tabFocus method introduced in the first PR, but never used.

Test Plan:
ninja && ninja check

Run src/qt/bitcoin-qt and check that all menu actions work.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7892