General cleanup and additional test coverage of WIP code.
* use enum for serveType
* combine instances of ServeConfig access within unset
* cleanMountPoint rewritten into cleanURLPath as it only handles URL paths
* refactor and test expandProxyTargetDev
> **Note**
> Behind the `TAILSCALE_USE_WIP_CODE` flag
updates #8489
Signed-off-by: Tyler Smalley <tyler@tailscale.com>
> **Note**
> Behind the `TAILSCALE_FUNNEL_DEV` flag
* Expose additional listeners through flags
* Add a --bg flag to run in the background
* --set-path to set a path for a specific target (assumes running in background)
See the parent issue for more context.
Updates #8489
Signed-off-by: Tyler Smalley <tyler@tailscale.com>
Tyler Smalley