Make TestingDirAuthVoteGuard/Exit/HSDir and AssumeReachable less essential in test networks

Currently, we need to use TestingDirAuthVoteGuard *, TestingDirAuthVoteExit *, and AssumeReachable 1 to get a test network to bootstrap in under a minute. With #8243 (moved), we may need to create a TestingDirAuthVoteHSDir * option as well.

These are rather blunt instruments to get boostrap working.

The changes in #13718 (moved) and (probably) #13929 (moved) ensure that testing networks bootstrap in 30s, without using TestingDirAuthVoteExit * or AssumeReachable 1. This provides a comprehensive method of testing network / exit bootstrap.

But it would be great to be able to test Guard/HSDir bootstrap too - perhaps by tweaking some settings in the chutney torrc_templates, or perhaps by fixing the implementation of one or more of tor's Testing... options (i.e. speeding up Guard/HSDir flag assignment in test networks).