Expose compiled_data APIs over FFI

[Manishearth]

There are a fair number of APIs that take TimeZoneProvider that I neglected to expose over FFI because I hadn't yet figured out how best to do TimeZoneProvider.

For now, we should expose all their compiled_data versions over FFI. E.g. temporal_capi::...::Instant should have a to_ixdtf_string() method, with a signature similar to https://github.com/boa-dev/temporal/blob/6cf05ae6dc286a23995a7094d586f57d291124b6/src/builtins/compiled/instant.rs#L12