skipruntime: add updateAll to write several input collections atomically

[skiplabsdaniel]

Updating N input collections required N calls to update, each triggering its own recomputation and its own round of subscriber notifications. Beyond the cost, subscribers observed intermediate states in which only part of the collections had been written, and a failure midway left the earlier writes applied.

Add updateAll, which writes a whole batch in one shot:

• writeInCollection (Runtime.sk) gains an update flag so several collections can be written before a single context.update() and a single getSubscriptions() drain -- one recomputation, one notification.
• SkipRuntime_Runtime__updateAll is exported from the FFI and wired through both the native addon and the wasm bindings, mirroring update.
• ServiceInstance.updateAll runs the batch in a fork, merged on success and aborted on failure, so the update is all-or-nothing.
• SkipServiceBroker.updateAll and the PATCH /v1/inputs control route expose it over HTTP, the batch counterpart of PATCH /v1/inputs/:collection.

Tests cover the batch on two services, assert that a batch produces exactly one subscriber notification where two sequential updates produce two, and check that a batch naming an unknown collection throws and leaves none of the collections written.