performance-metrics: Move some helper functions to test_infra

The helper functions for measuring and parsing the performance of
virtio-net and virtio-block devices are moved to the `test_infra` crate
so that they be reused for integration tests of rate limiter.

Signed-off-by: Bo Chen <chen.bo@intel.com>

test_infra/Cargo.toml

@@ -9,6 +9,8 @@ dirs = "4.0.0"
 epoll = "4.3.1"
 libc = "0.2.132"
 once_cell = "1.14.0"
+serde = { version = "1.0.144", features = ["rc", "derive"] }
+serde_json = "1.0.85"
 ssh2 = { version = "0.9.3", features = ["vendored-openssl"] }
 vmm-sys-util = "0.10.0"
 wait-timeout = "0.2.0"