This pulls out the Wake-on-LAN (WoL) code out into its own package
(feature/wakeonlan) that registers itself with various new hooks
around tailscaled.
Then a new build tag (ts_omit_wakeonlan) causes the package to not
even be linked in the binary.
Ohter new packages include:
* feature: to just record which features are loaded. Future:
dependencies between features.
* feature/condregister: the package with all the build tags
that tailscaled, tsnet, and the Tailscale Xcode project
extension can empty (underscore) import to load features
as a function of the defined build tags.
Future commits will move of our "ts_omit_foo" build tags into this
style.
Updates #12614
Change-Id: I9c5378dafb1113b62b816aabef02714db3fc9c4a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick