feat(compiler): allow flexible spacing in v-for

[jh-leong]

Close #6499.

Previously, spaces around 'of' were required, but with this change, it is now possible to write v-for without the spaces.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	90 kB	34.5 kB	31.1 kB
vue.global.prod.js	147 kB (+98 B)	54 kB (+34 B)	48.1 kB (+7 B)

Usages

Name	Size	Gzip	Brotli
createApp	49.8 kB	19.5 kB	17.8 kB
createSSRApp	53.3 kB	21 kB	19.1 kB
defineCustomElement	52 kB	20.3 kB	18.5 kB
overall	63.3 kB	24.5 kB	22.3 kB

[baiwusanyu-c]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
nuxt	✅ success	✅ success
pinia	✅ success	✅ success
quasar	✅ 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	❌ failure	❌ failure
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success

[jh-leong]

The changes in this PR have fixed #5819. Updated the test cases to reflect this fix.