fix(runtime-dom): prevent unnecessary updates in v-model checkbox when value is unchanged

[jh-leong]

close #12144

In the browser, the event order for an input click is click -> change.

When the click event has side effects, vModelCheckbox's beforeUpdate hook updates el.checked based on the old binding, causing it to reset incorrectly. The change event then updates the binding with the wrong value, leading to the issue.

This PR ensures el.checked is only updated when the binding changes, fixing a 3.5 regression and restoring 3.4 behavior.

NOTE: This PR only addresses cases where the value is neither an array nor a set (issue #8638 is still unhandled).

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB (+47 B)	38.2 kB (+14 B)	34.3 kB (+19 B)
vue.global.prod.js	160 kB (+47 B)	58.1 kB (+18 B)	51.6 kB (+12 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	49.2 kB	19 kB	17.3 kB
createApp	55.8 kB	21.5 kB	19.6 kB
createSSRApp	59.8 kB	23.2 kB	21.1 kB
defineCustomElement	60.6 kB	23.1 kB	21 kB
overall	69.5 kB	26.6 kB	24.2 kB

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vue

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commit: 6e77a7f

[jh-leong]

/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	✅ success	✅ success
vuetify	✅ success	✅ success
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success

[skirtles-code]

Potentially a fix for #8638.

[skirtles-code]

I think this fix may suffer from a similar problem to #8639:

• Playground - this PR
• Playground - 3.5.11