97c112d4ca Declare TorReply parsing functions in torcontrol_tests (Ben Woosley)

Pull request description:

These methods are standalone string parsing methods which were included
into test via an include of torcontrol.cpp, which is bad practice.

~~Splitting them out reveals that they were the only torcontrol.cpp
methods under test, so the test file is renamed tor_reply_tests.cpp.~~

Introduced in #10408

Tree-SHA512: 8ff11a9c900a88f910a73dfe16f43581a567e9d60e9298a8a963fc9dd7cffb4d97a644da677610aafb7d89f1dd1cede9afeae2c6344305e021a9a322dbcea0ac

Backport of Core PR13291
https://github.com/bitcoin/bitcoin/pull/13291/

Depends on D3293

Should be landed immediately after dependency