fix(ssr): use observable-membrane's read-only proxy

[nolanlawson]

Details

Fixes #4799

We actually have 2 fewer test failures than before, and the read-only tests pass before and after, so this means I was way overthinking it when I did #4779.

Does this pull request introduce a breaking change?

• 😮‍💨 No, it does not introduce a breaking change.

Does this pull request introduce an observable change?

• 🤞 No, it does not introduce an observable change.

[nolanlawson]

These are the 2 fixed tests:

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[13/45]⎯

 FAIL  |lwc-ssr-compiler| src/__tests__/fixtures.spec.ts > fixtures > known-boolean-attributes/incorrect-tag-attr-pair/dynamic/index.js
Error: Snapshot `fixtures > known-boolean-attributes/incorrect-tag-attr-pair/dynamic/index.js 1` mismatched

- Expected
+ Received

+ Cannot convert object to primitive value

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[14/45]⎯

 FAIL  |lwc-ssr-compiler| src/__tests__/fixtures.spec.ts > fixtures > known-boolean-attributes/default-def-html-attributes/dynamic/index.js
Error: Snapshot `fixtures > known-boolean-attributes/default-def-html-attributes/dynamic/index.js 1` mismatched

- Expected
+ Received

+ Cannot convert object to primitive value

[nolanlawson]

Gets bundled into the dist file FWIW