feature: Add multi-node connection pool (#189)

* Implement static node list connection pool
* trait for setting connection distribution. Defaults to RoundRobin.
* Allow reseeding of nodes on MultiNodeConnection
* Implement Sniff Nodes request

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Co-authored-by: Stephen Leyva <sleyva1297@gmail.com>
Co-authored-by: Sylvain Wallez <sylvain@elastic.co>

elasticsearch/Cargo.toml

@@ -36,6 +36,7 @@ url = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 serde_with = "3"
+tokio = { version = "1", default-features = false, features = ["macros", "net", "time", "rt-multi-thread"] }
 void = "1"
 
 [dev-dependencies]
@@ -50,7 +51,6 @@ os_type = "2"
 regex="1"
 #sysinfo = "0.31"
 textwrap = "0.16"
-tokio = { version = "1", default-features = false, features = ["macros", "net", "time", "rt-multi-thread"] }
 xml-rs = "0.8"
 
 [build-dependencies]