[FEATURE] StreamClass-based contracts

[s-vitaliy]

The streaming plugins and the stream operator utilize a specific set of entities that must be consistent across both applications. These include:

• The value of schema mismatch annotation
• The structure of the stream status resource

These aspects are planned to be updated in future versions of Arcane Operator as follows:

• The Stream class resource will incorporate additional fields that provide a description of the schema mismatch reporting mechanism.
• The Stream class resource will include extra fields that explain the structure of the stream status resource.

[s-vitaliy]

Also if the stream plugin cannot run in backfill mode, it should be defined in StreamClass.

[s-vitaliy]

Also, stream class should provide configuration for retries (see: #124)