[cdc_stream] Add a CLI client to start/stop asset streaming sessions (#4)

Implements the cdc_stream client and adjusts asset streaming in
various places to work better outside of a GGP environment.

This CL tries to get quoting for SSH commands right. It also brings
back the ability to start a streaming session from
asset_stream_manager.

Also cleans up Bazel targets setup. Since the sln file is now in root,
it is no longer necessary to prepend ../ to relative filenames to
make clicking on errors work.

tests_asset_streaming_30/BUILD

@@ -28,6 +28,7 @@ cc_binary(
         "//asset_stream_manager:multi_session",
         "//cdc_fuse_fs:asset",
         "//cdc_fuse_fs:cdc_fuse_fs_lib_mocked",
+        "//cdc_fuse_fs:mock_config_stream_client",
         "//common:test_main",
         "//common:testing_clock",
         "//data_store:data_provider",