Include RUNTIME_METADATA_HASH in cache key (#4476)

Add RUNTIME_METADATA_HASH variable to
[`cache.extraEnv`](https://github.com/paritytech/forklift/tree/0.12.4?tab=readme-ov-file#cache)
in config.toml (setting available from forklift 0.12.4)

Author: AndWeHaveAPlan

.forklift/config.toml

@@ -10,6 +10,9 @@ jobsBlackList = []
 logLevel = "warn"
 threadsCount = 6
 
+[cache]
+extraEnv = ["RUNTIME_METADATA_HASH"]
+
 [metrics]
 enabled = true
 pushEndpoint = "placeholder"