fix(compiler-core): allow unicode to appear in simple identifiers

[godxiaoji]

fix #6367

I refer to #3443 .

[skirtles-code]

I commented on this previously, but that comment has been incorrectly marked as resolved.

I believe this PR still needs a test adding. The test that has been included doesn't seem to be related to the change.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	90.8 kB	34.5 kB	31.1 kB
vue.global.prod.js	148 kB (+11 B)	53.7 kB (+1 B)	48 kB (+19 B)

Usages

Name	Size	Gzip	Brotli
createApp	50.8 kB	19.9 kB	18.1 kB
createSSRApp	54.1 kB	21.2 kB	19.3 kB
defineCustomElement	53.1 kB	20.6 kB	18.8 kB
overall	64.6 kB	24.9 kB	22.6 kB

[godxiaoji]

I commented on this previously, but that comment has been incorrectly marked as resolved.

I believe this PR still needs a test adding. The test that has been included doesn't seem to be related to the change.

I have submitted a new test, please review it again.