Initial DNS proxy implementation

This copies much of the logic from Istio, however it also supports a multi-tenant proxy.

## New crate

The new `istio-dns` crate extends the Trust-DNS API to specifically support the DNS proxy use case. The existing Trust-DNS `Catalog` does not allow an `Authority` to conditionally indicate its answers as authoritative, which is something that a proxy needs to do. The code here was written with the intent of eventually upstreaming to Trust-DNS.

## Host aliases

Within ztunnel, a new `dns` package implements the `istio-dns` `Resolver`, and serves DNS directly from the `WorkloadStore`.

The logic for handling host aliases has been somewhat inverted from Istio. Istio pre-generated aliases for each client and added entries for all possible hosts to the lookup table.

However, in shared proxy mode we have to handle the problem that some host aliases are client-specific (e.g. just service-name without namespace). To account for this, we dynamically run the alias logic in reverse, trying to figure out the FQDN from the requested hostname. This means that no additional entries for aliases were necessary in the `WorkloadStore`.

## Forwarding

Ztunnel dns uses one of two types of DNS forwarders, depending on if shared or dedicated mode. When in shared mode, it needs to use the configuration for the client pod in order to forward to the appropriate upstream resolver.

Fixes #487

Cargo.toml

@@ -78,6 +78,13 @@ tower-hyper-http-body-compat = { version = "0", features = ["server", "http2"] }
 futures-util = "0.3.26"
 chrono = "0.4.23"
 
+# DNS
+istio-dns = { version = "0.0.0", path = "crates/dns" }
+trust-dns-client = "0.22.0"
+trust-dns-proto = "0.22.0"
+trust-dns-server = "0.22.0"
+trust-dns-resolver = "0.22.0"
+
 [target.'cfg(target_os = "linux")'.dependencies]
 netns-rs = "0.1.0"
 
@@ -102,6 +109,7 @@ incremental = true
 [dev-dependencies]
 criterion = { version = "0.4.0", features = ["async_tokio", "html_reports"] }
 diff = "0.1.13"
+istio-dns = { version = "0.0.0", path = "crates/dns", features = [ "testing" ] }
 matches = "0.1.9"
 test-case = "3.0.0"
 #debug = true