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

Depends on D4275

In your make build dir:

../configure
make check
../configure --with-seeder=false
make check

seeder_tests.cpp should not show up during testing

ls src/seeder/

This should only show the test/ directory.

ls src/seeder/test

This should show nothing.

In your cmake build dir:

cmake -GNinja ..
ninja check

rm -r ./*

You can skip this step, but there will be leftover seeder directory and files in the next part if you do.

cmake -GNinja -DBUILD_BITCOIN_SEEDER=OFF ..
ninja check
ls src

There should be no seeder directory. If you skipped the rm -r ./* step then you can verify with:

ls -al src
src/test/test_bitcoin --run_test=parse_name_simple

The seeder directory should have an earlier time stamp than everything else.
The command should fail with the following error message:

Test setup error: no test cases matching filter or all test cases were disabled