fix(runtime-dom): ensure only symbols are explicitly stringified during attribute patching

[LinusBorg]

This covers an edge case where a web component actually overrides el.setAttribute and thus is able to receive non-string values as attribute values (appareantly, extJS web components do this).

This patch ensures that we leave stringification to the browser when patching an element attribute except for the case of symbols, where we need to explicitly stringify it ourselves as the browser would throw an error.

fix: #11177

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	89.6 kB (+7 B)	34.2 kB (+4 B)	30.9 kB (+8 B)
vue.global.prod.js	146 kB (+7 B)	53.6 kB (+5 B)	47.8 kB (-9 B)

Usages

Name	Size	Gzip	Brotli
createApp	51.6 kB (+7 B)	20.2 kB (+5 B)	18.3 kB (-4 B)
createSSRApp	54.9 kB (+7 B)	21.5 kB (+7 B)	19.6 kB (+13 B)
defineCustomElement	53.9 kB (+7 B)	20.9 kB (+5 B)	19 kB (+5 B)
overall	65.3 kB (+7 B)	25.2 kB (+7 B)	22.8 kB (+2 B)

[LinusBorg]

I think this patch is worthwhile, but I want to mention that this is an edge case for specific web component implementations, and the typeof might add a (small, likely neglectable) perf overhead when patching a lot of attributes.