merge back

…608, #673, #676, #681, #690, #697, #717, #757, #751, #773, #801 (qt backports: part 4)

a41f4e7 merge bitcoin-core/gui#801: Fix nullptr clientModel access during shutdown (Kittywhiskers Van Gogh)
56fc672 merge bitcoin-core/gui#773: Check for private keys disabled before attempting unlock (Kittywhiskers Van Gogh)
ae0ca10 merge bitcoin-core/gui#751: macOS, do not process actions during shutdown (Kittywhiskers Van Gogh)
107a180 merge bitcoin-core/gui#757: Add wallet name to address book page title (Kittywhiskers Van Gogh)
9385d44 merge bitcoin-core/gui#717: Use the stored CSubNet entry when unbanning (Kittywhiskers Van Gogh)
fd651ee merge bitcoin-core/gui#697: Remove reindex special case from the progress bar label (Kittywhiskers Van Gogh)
8bdcd12 merge bitcoin-core/gui#690: Catch invalid networks combination crash (Kittywhiskers Van Gogh)
6cc422d merge bitcoin-core/gui#681: Fix Transaction Relay tooltip text in Peers details window (Kittywhiskers Van Gogh)
5c894e1 merge bitcoin-core/gui#676: Update peers window "Transaction Relay" label and tooltip (Kittywhiskers Van Gogh)
13990d8 merge bitcoin-core/gui#673: Use fallback value for Version and User Agent during peer connection (Kittywhiskers Van Gogh)
320f0e6 merge bitcoin-core/gui#608: Make `WalletModel::sendCoins()` return `void` (Kittywhiskers Van Gogh)
bb5b44e merge bitcoin-core/gui#581: Revamp `ClientModel` code to handle core signals (Kittywhiskers Van Gogh)
a334b68 merge bitcoin-core/gui#590: Declare `WalletModel` member functions with `const` (Kittywhiskers Van Gogh)
212e54d merge bitcoin-core/gui#556: Make BitcoinUnits::Unit a scoped enum (Kittywhiskers Van Gogh)
27951a3 merge bitcoin-core/gui#552: Refactor `TransactionDesc::FormatTxStatus` and `TransactionStatus` (Kittywhiskers Van Gogh)
054ffdb merge bitcoin-core/gui#557: revert bitcoin-core/gui#296 (Kittywhiskers Van Gogh)

Pull request description:

  ## Additional Information

  * Even though "DiplayBitcoinUnit" has been Dashified, the associated value is not (see below, from `~/.config/Dash/Dash-Qt-testnet.conf`) as renaming "BitcoinUnit" would cause significant conflicts when backporting, so it has retained its upstream name.

    ```
    DisplayDashUnit=@variant(\0\0\0\x7f\0\0\0\x13\x42itcoinUnits::Unit\0\0)
    ```

  * [bitcoin-core/gui#581](bitcoin-core/gui#581) affects three Dash-specific signal handlers, `m_handler_notify_additional_data_sync_progess_changed`, `m_handler_notify_chainlock` and `m_handler_notify_masternodelist_changed` and their refactoring needs to be specially reviewed.

  ## Breaking Changes

  None expected.

  ## Checklist

  - [x] I have performed a self-review of my own code **(note: N/A)**
  - [x] I have commented my code, particularly in hard-to-understand areas **(note: N/A)**
  - [x] I have added or updated relevant unit/integration/functional/e2e tests
  - [x] I have made corresponding changes to the documentation **(note: N/A)**
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  UdjinM6:
    light ACK a41f4e7

Tree-SHA512: 85e683beb2548e8d47a5c52b1ff802711b53c4432435f52c146ef6774edac6604fbc08365554ce23084bfb26f6ab9358df6ccae3d869c625510098cb3efc1471