Add simple unit tests for parse_name()

Summary:
Adds some simple unit tests for the seeder's parse_name() function.

Currently, parse_name() has some logic flaws that prevent some test cases.

• No check for the length of the query name (the maximum length is 255 characters total)
• An assumption that the length of the output buffer is greater than 0.

Depends on D4417

Test Plan:

make check
ninja check

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

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4418