Gracefully handle panics in all request handlers

[http.Server](https://pkg.go.dev/net/http#Server) handles panics in request handler goroutines using `recover`, but other servers used by Consul do not. By handling panics in request handlers we will prevent any panics in request handlers from shutting down the entire process.

* [x] HTTP API should already work correctly because `http.Server` handles panics
* [x] #10895 XDS `grpc.Server` can use [grpc-middleware/recover](https://pkg.go.dev/github.com/grpc-ecosystem/go-grpc-middleware/v2@v2.0.0-rc.2/interceptors/recovery) (or an interceptor with a similar implementation)
* [x] #10895 Server RPC `grpc.Server` can use the same
* [ ] the Server port has [many services behind it](https://github.com/hashicorp/consul/tree/main/contributing/rpc#routing). `Server.handleConsulConn` can recover from most, but we should also look at `Server.handleSnapshotConn` and `Server.handleInsecureConn` and probably do the same there.
* [ ] DNS interface - unknown. needs investigation

Start with Server.handleSnapshotConn and Server.handleInsecureConn, alongside the existing Server.handleConsulConn recovery path. Investigate the DNS interface separately, then verify that all request-handler paths recover panics without shutting down the process; the issue does not identify a test file.

Written by the indexing model from the issue text.