Rewrite xapian-bridge in C

This commit ports xapian-bridge from GJS to C. The port is meant as a
drop-in replacement for the former code, with 1:1 compatibility.
Convert tests to gtest

Convert our unit tests to C tests using GLib's gtest.
Remove eos-jasmine submodule

Now that our tests are in C, we don't need this anymore.
Update .gitignore