GitLab

* move some code around

* remove num_backends parameter from XdsEnd2endTest

* remove use_xds_enabled_server param from XdsEnd2endTest

* remove xds_resource_does_not_exist_timeout_ms param from XdsEnd2endTest

* remove client_load_reporting_interval_seconds param from XdsEnd2endTest

* start moving CreateAndStartBackends() into individual tests

* finish moving CreateAndStartBackends() into individual tests

* remove unused variable

* remove SetEdsResourceWithDelay

* fix test flake

* clang-tidy

* clang-format

* move test framework to its own library

* fix build

* clang-format

* fix windows build

* rename TestType to XdsTestType

* move BackendServiceImpl inside of BackendServerThread

* clang-format

* move AdminServerThread to CSDS test suite

* remove unnecessary deps