Fix wallet RPC race by waiting for callbacks in sendrawtransaction

Summary:
This is partial backport of Core PR10286 : https://github.com/bitcoin/bitcoin/pull/10286/commits/cb06edf938302166030db19017c27889ea5b10b6

This patch was merged with the following bug fix:

Fix sendrawtransaction hang when sending a tx already in mempool

This is a backport of Core PR11738 : https://github.com/bitcoin/bitcoin/pull/11738

Test Plan:

make check
./test/functional/test_runner.py --extended

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D3165