Migrate proxy logic to the API package (#4216)

This allows arbitrary programs to have an easy mechanism to make
connections through Boundary using Go. Internal cluster tests and test
helpers have been migrated to use this package, as well as the `connect`
command.

---------

Co-authored-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>

api/go.mod

@@ -10,14 +10,19 @@ require (
 	github.com/hashicorp/go-kms-wrapping/v2 v2.0.14
 	github.com/hashicorp/go-retryablehttp v0.7.4
 	github.com/hashicorp/go-rootcerts v1.0.2
+	github.com/hashicorp/go-secure-stdlib/base62 v0.1.2
 	github.com/hashicorp/go-secure-stdlib/parseutil v0.1.8
+	github.com/hashicorp/go-secure-stdlib/temperror v0.1.1
 	github.com/hashicorp/go-uuid v1.0.3
+	github.com/mitchellh/copystructure v1.2.0
 	github.com/mitchellh/mapstructure v1.5.0
 	github.com/mr-tron/base58 v1.2.0
 	github.com/stretchr/testify v1.8.4
+	go.uber.org/atomic v1.11.0
 	golang.org/x/time v0.3.0
 	google.golang.org/grpc v1.59.0
 	google.golang.org/protobuf v1.31.0
+	nhooyr.io/websocket v1.8.10
 )
 
 require (
@@ -29,11 +34,11 @@ require (
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/hashicorp/go-secure-stdlib/strutil v0.1.2 // indirect
 	github.com/hashicorp/go-sockaddr v1.0.5 // indirect
-	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/pointerstructure v1.2.1 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rogpeppe/go-internal v1.8.1 // indirect
 	github.com/ryanuber/go-glob v1.0.0 // indirect
 	golang.org/x/crypto v0.14.0 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20231030173426-d783a09b4405 // indirect