Pipelined cycle schema reading

[roxblnfk]

Q	A
New feature?	✔️
Breaks BC?	❌

SchemaProviderInterface now contains only read and clear schema related methods, and read() method changed to read(?SchemaProviderInterface $nextProvider = null).
SchemaManager is deprecated (should be removed later).

Now there is no need to force to write the schema from the outside. Each provider can decide this on their own.
It also allows the provider to change the schema he received from the $nextProvider.

• check RU documentation changes
• update EN documentation en doc update roxblnfk/yii-cycle#3

[samdark]

@roxblnfk feel free to merge it when ready.

[samdark]

👍