test: cover admin functionality of Trigger

[SnoopJ]

Description

Closes #2734 by adding a new test that checks that Trigger.admin is correct for a basic PRIVMSG. Could be expanded for other types of messages but I figured this was a good start.

Checklist

• I have read CONTRIBUTING.md
• I can and do license this contribution under the EFLv2
• No issues are reported by make qa (runs make lint and make test)
• I have tested the functionality of the things this change touches

[dgw]

This is getting at what I meant here about "discretizing" different cases.

Parametrized tests make each combination a unique test that can pass or fail independently, which I (at least) find helpful when something regresses. That's great :)

I would just ask you to consider adding nick-only matching to this matrix for completeness. Possibly also wildcard handling, since that's a feature of the underlying pattern generator:

sopel/sopel/tools/__init__.py

Lines 82 to 93 in f8d536d

	def get_hostmask_regex(mask):
	"""Get a compiled regex pattern for an IRC hostmask
	:param str mask: the hostmask that the pattern should match
	:return: a compiled regex pattern matching the given ``mask``
	:rtype: :ref:`re.Pattern <python:re-objects>`
	.. versionadded:: 4.4
	"""
	mask = re.escape(mask)
	mask = mask.replace(r'\*', '.*')
	return re.compile(mask + '$', re.I)