Fix code search when text is larger than max gRPC message size

Modifies gitaly client to support chunking of search files response

In gitaly!1015 (merged), we add the ability to stream file search matches back in a chunked manner. This MR changes the gitaly client to take advantage of this new behavior

What are the relevant issue numbers?

• gitaly#1377 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer