Merge bitcoin-core/gui#471: Add Wallet Restore in the GUI

bc13ec888c doc: Add a release note about the "restore wallet" menu item (w0xlt)
e7a3f698b5 gui: Add Wallet Restore in the GUI (w0xlt)

Pull request description:

  This PR adds a menu item to restore a wallet from a backup file in the GUI.
  Currently this option exists only in RPC interface.

  Motivation: It makes easier for non-technical users to restore backups.

  Master | PR |
  --- | ---
  <img width="307" alt="master" src="https://user-images.githubusercontent.com/94266259/141673349-0bf8a237-ecec-42e4-a0d7-1d5863940036.png"> | <img width="307" alt="pr" src="https://user-images.githubusercontent.com/94266259/141673350-972dea23-ae56-4283-a365-819da62b7067.png"> |

ACKs for top commit:
  w0xlt:
    Added a release note in a new commit (bc13ec888c) to not invalidate the ACKs for the previous one.
  furszy:
    utACK bc13ec8
  shaavan:
    ACK bc13ec888c
  hebasto:
    ACK bc13ec888c

Tree-SHA512: edc3675484238857b77e74382a4041dd5d2cbcda1e2d5bfe52c83d9d7bb7be8a243ecd97e25e994d8c30ab6d7c59ead5a1c953a46dce173666b137eeffc3c94f

doc/release-notes/release-notes-471.md

@@ -0,0 +1,4 @@
+GUI changes
+--------
+
+- A new menu item to restore a wallet from a backup file has been added (#471).