fix(scheduler): ensure recursive jobs can't be queued twice

[skirtles-code]

This PR was originally going to be just tests for #11826, which was merged a couple of weeks ago. But while working on the tests I realised there was a small bug in my original PR, which I've fixed here.

In my original fix, I assumed that it was safe to clear the QUEUED flag unconditionally after a job had run. However, this isn't always correct for jobs with ALLOW_RECURSE.

For a job with ALLOW_RECURSE, the QUEUED flag is already cleared before the job runs. If the job does recurse then the QUEUED flag will be set again. In that scenario it shouldn't be cleared after the job runs. Mistakenly clearing the flag allows the job to be added to the queue again.

In practice, even if the job does get queued twice, the dirtiness checks should significantly limit its impact. The 'Maximum recursive updates' warning could be hit prematurely, but as the bug only allows the job to be queued twice it would still need to recurse several times to hit that warning.

While the bug is low impact, it's also an easy fix.

There is some duplication between flushJobs and flushPreFlushCbs. I may investigate refactoring that later, but I didn't want to complicate this PR with a refactoring.

The tests cover various scenarios for both this fix and the original fix in #11826.

This PR only considers the main scheduler queue, not the post queue. The post queue does still need tests writing for #11826, but there are various other edge cases I need to think through before I attempt that. It uses a Set to de-duplicate jobs, so it isn't impacted by the bug I've fixed here.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB (+24 B)	37.9 kB (+3 B)	34.1 kB (-28 B)
vue.global.prod.js	159 kB (+24 B)	57.8 kB (+3 B)	51.3 kB (-64 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	48.8 kB (+24 B)	18.8 kB (+8 B)	17.2 kB (+12 B)
createApp	55.4 kB (+24 B)	21.3 kB (+8 B)	19.4 kB (+15 B)
createSSRApp	59.4 kB (+24 B)	23 kB (+5 B)	21 kB
defineCustomElement	60.2 kB (+24 B)	22.9 kB (+9 B)	20.8 kB (-48 B)
overall	69.1 kB (+24 B)	26.4 kB (+4 B)	24 kB (+1 B)

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commit: a776c1a

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
nuxt	✅ success	✅ success
pinia	✅ success	✅ success
primevue	✅ success	✅ success
quasar	✅ success	✅ success
radix-vue	✅ success	✅ success
router	✅ success	✅ success
test-utils	✅ success	✅ success
vant	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vue-macros	❌ failure	❌ failure
vuetify	✅ success	✅ success
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success