Add DB activity based routing (#864)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pgcat"
-version = "1.2.0"
+version = "1.3.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
@@ -55,6 +55,10 @@ tracing-subscriber = { version = "0.3.17", features = [
     "std",
 ] }
 lru = "0.12.0"
+mini-moka = "0.10.3"
 
 [target.'cfg(not(target_env = "msvc"))'.dependencies]
 jemallocator = "0.5.0"
+
+[dev-dependencies]
+serial_test = "*"