Fix js_top_worker to build with oxcaml compiler
The oxcaml compiler changed cmi_crcs from (string * Digest.t option) list
to Import_info.t array, and Env.crc_of_unit now takes Compilation_unit.Name.t
instead of string. Update all three call sites accordingly.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>