class WatchClockRecoveryPositionInfo

Gets the ring buffer current position via a hanging get.

`WatchClockRecoveryPositionInfo` may only be called after `GetVmo` was called, where a

`clock_recovery_notifications_per_ring` was specified.

The driver must respond to a client's first `WatchClockRecoveryPositionInfo` call, but will

not respond to subsequent client calls until the position information has changed from what

was most recently provided to that client.

The driver must not respond to a `WatchClockRecoveryPositionInfo` until after it has replied

to the `Start` command.

At the `start_time` returned by `Start`, position is always 0. From there, it

progresses at the rate specified by the rate, sample format (and clock domain,

if the device is not in the same clock domain as`CLOCK_MONOTONIC`).

If `clock_recovery_notifications_per_ring` is not zero, the driver will reply with its

estimated position to be used for clock recovery at most at

`clock_recovery_notifications_per_ring` frequency.

The `RingBufferPositionInfo` return values must include timestamps that are monotonically

increasing.

The driver will close the protocol channel with an error of `ZX_ERR_BAD_STATE`, if there is

already a pending `WatchClockRecoveryPositionInfo` for this client.