Reland "Cronet: add test server"

This reverts commit a0fdf1e70ea30b16c26f80143d8af9ed60c6b33f.

Reason for revert: Should work now after aosp/2314940
Also removes usage of the added test server

Test: atest CtsCronetTestCases
Change-Id: I1cde8ab8205c7ed12ce97ba6e9580c9b8c333053
5 files changed