This merges `osd` API into `machined`. API was copied from `osd` into
`machined`, and `osd` API was deprecated.
For backwards compatibility, `machined` still implements `osd` API, so
older Talos API clients can still talk to the node without changes.
Docs were updated. No functional changes.
Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>