search: export ZoektGlobalQuery fields

Created by: rvantonder

Stacked on https://github.com/sourcegraph/sourcegraph/pull/36514.

The global Zoekt query values (like pattern) are not output when printed because the fields are unexported. These are pretty important test values for upcoming lucky search and I can't easily check correctness without exporting these.

Test plan

Semantics-preserving.