runtime-api/workers getAllProviders() incorrect implementation

[mnaamani]

The getAllProviders() method should return an array of worker ids of storage providers. The current implementation incorrectly includes all worker ids without filter out the lead worker id.

I observed this while running helios and knowing there was only one live storage provider.

[mnaamani]

This lead worker id should not be treated any differently in-fact and the implementation is correct.
What should be changed however is the selection of liaison by the runtime, which for some reason excludes the lead:

joystream/runtime/src/integration/storage.rs

Line 11 in 1c6d7e2

let ids = crate::StorageWorkingGroup::get_regular_worker_ids();

[mnaamani]

Done in #1234