[backport#13966] gui: Show watch-only eye instead of HD disabled

Summary:
https://github.com/bitcoin/bitcoin/pull/13966/commits/82d6c5aad330bb06d0c918b4e9304c25ff2bdcc8

Depends on D7300

Concludes backport of Core PR13966

Test Plan:

ninja check
./src/qt/bitcoin-qt -testnet

open a watch-only wallet. see that the HD icon has been replaced by The Eye

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7301