Merge #19756: tests: add sync_all to fix race condition in wallet groups test

Summary:
72ae20fc142457a200278cb2fedc5e32a3766b58 tests: add sync_all to fix race condition in wallet groups test (Karl-Johan Alm)

Pull request description:

This most likely fixes #19749, the intermittent CI issues with wallet_groups.

This fix is also included in #19743.

Backport of Core PR19756

We're seeing increased flakiness for this test in our sanitizer builds. This should fix it.

Test Plan: ./test/functional/test_runner.py wallet_groups

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7826