Revert "Drop minimum fee to 250sat/kb" and "Use a modified size for transaction minimum fee calculation."

Summary:
This reverts commit a05062890a9c2401e0b5a0da2b24434d9886eaac.
This reverts commit b983ebdcaba0fdbf4e04ce2cc7f197e1086058a8.

These commit break seveeral extended tests.

Test Plan:

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

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1482