Compile against a large corpus of files in our tests to assert there are no exceptions

[olafurpg]

Following up from https://github.com/sourcegraph/lsif-java/pull/182

This bug got caught during manual testing. It would have been nice to catch it when the new annotation support got added. One thing we can do is to extend our test suite to index a large corpus of files and assert that there are no unexpected errors. We don't care about the generated SemanticDB, only that the plugin doesn't crash during compilation.