test: improve test coverage

[sun0day]

Description

All PRs from this branch intend to increase UT coverage and optimize vueuse source code. I will continuously commit test code to this branch.

All commits in this branch are atomic, feel free to merge PR at any time.@antfu

History PRs:

• test: impove test coverage #2185
• test: improve test coverage #2233
• test: improve test coverage #2256

Updated UT Coverage

api	statements	branches	functions	lines
refAutoReset	100% ⬆️	100%	100% ⬆️	100% ⬆️
useRefHistory	100% ⬆️	100% ⬆️	100% ⬆️	100% ⬆️
useFirestore	100% ⬆️	100% ⬆️	100% ⬆️	100% ⬆️
syncRefs	100% ⬆️	100%	100% ⬆️	100% ⬆️
useTimeoutPoll	100% ⬆️	100% ⬆️	100%	100% ⬆️
usePointerSwipe	100% ⬆️	100% ⬆️	100% ⬆️	100% ⬆️

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Test

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.