ZJIT: Optimize lookups from frozen instances/frozen classes

[tekknolagi]

• Array length
• String length/bytesize
• Anything that results from toregexp
• Symbols

[tekknolagi]

Still need ArrayLength, string stuff, ...

[tekknolagi]

Maybe another TODO here would be to avoid clearing LoadField from frozen objects in load-store forwarding static analysis

cc @jacob-shops