Merge #10587: Net: Fix resource leak in ReadBinaryFile(...)

Summary:
f2fb132cb Net: Fix resource leak in ReadBinaryFile(...) (practicalswift)

Tree-SHA512: 879b9334d8bb681fa4b6f96d8ecb54e2a8948065f7be5fe7880131479c813602fc9d4a4314f043e6591e1aed50ffafa7c247362a9cdeb049b0721170e227b89a

Backport of Core PR10587
https://github.com/bitcoin/bitcoin/pull/10587

Dependent on D3283

Completes T613

This should land immediately after its dependency.

Test Plan:

make check
test_runner.py

Reviewers: jasonbcox, deadalnix, Fabien, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3285