refactor(core): Reduce verbosity of binding core functions

[AaronO]

Removes boilerplate in bindings::initialize_context() when setting core functions, improving readability.

initialize_context() is shortened from 98 to 36 lines, making the core logic easier to grasp.

[CLAassistant]

All committers have signed the CLA.

[AaronO]

Slightly longer after rustfmt expanded the setMacrotaskCallback line, but point still stands.

On that note, should 80 still be the max-width ? I know the linux kernel recently relaxed their max-width to 100, might be worth considering (but it's minor at the end of the day, no point bikeshedding)

[bartlomieju]

LGTM, thanks @AaronO