[wallet] Remove CAccountingEntry class

Summary:
No longer used

Partial backport of Core PR13825
https://github.com/bitcoin/bitcoin/pull/13825/commits/7c6f1a1f954512a7dab70e6e0e856a199584b168

Depends on D5411, D5412, D5413, D5414, D5415, D5416

Test Plan:

ninja check
test_runner.py wallet_*

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D5418