MSSQL: Minor refactor (#113976)

* Moving things around

* Copy parseURL function to where it's used

* Update test

* Remove experimental-strip-types

* Revert "Remove experimental-strip-types"

This reverts commit 70fbc1c0cd.

* Trigger build

pkg/tsdb/mssql/sqleng/proxy.go

@@ -0,0 +1,33 @@
+package sqleng
+
+import (
+	"context"
+	"errors"
+	"net"
+
+	mssql "github.com/microsoft/go-mssqldb"
+	"golang.org/x/net/proxy"
+)
+
+type HostTransportDialer struct {
+	Dialer proxy.ContextDialer
+	Host   string
+}
+
+func (m HostTransportDialer) HostName() string {
+	return m.Host
+}
+
+func (m HostTransportDialer) DialContext(ctx context.Context, network string, addr string) (conn net.Conn, err error) {
+	return m.Dialer.DialContext(ctx, network, addr)
+}
+
+// // we wrap the proxy.Dialer to become dialer that the mssql module accepts
+func newMSSQLProxyDialer(hostName string, dialer proxy.Dialer) (mssql.Dialer, error) {
+	contextDialer, ok := dialer.(proxy.ContextDialer)
+	if !ok {
+		return nil, errors.New("unable to cast socks proxy dialer to context proxy dialer")
+	}
+
+	return &HostTransportDialer{contextDialer, hostName}, nil
+}