bun:ffi: infer exact signatures from symbol definitions, fix cc argument/return conversions - #32075

Running Vale across on the following files affected by this PR:

- runtime/ffi.mdx

Attempting to initialize Vale linter...
No customer vale configuration detected. Using Mintlify's default configuration.
Attempting to run Vale spellcheck...
Vale spellcheck completed successfully.

docs/runtime/ffi.mdx:
	- 15:4      Did you really mean 'dlopen'?
	- 36:24     Did you really mean 'cstring'?
	- 72:72     Did you really mean 'dlopen'?
	- 148:3     Did you really mean 'napi_env'?
	- 149:3     Did you really mean 'napi_value'?
	- 225:96    Did you really mean 'napi'?
	- 313:25    Did you really mean 'JSCallback'?


Found 7 suggested changes across 1 files in 639.03ms