[WIP] Drive per-sample external source with batch size from batched ones.

[mzient]

Signed-off-by: Michał Zientkiewicz [email protected]

Why we need this PR?

Pick one, remove the rest

• It fixes a bug: per-sample external source don't adjust to dynamic batch size

What happened in this PR?

Fill relevant points, put NA otherwise. Replace anything inside []

• What solution was applied:
  • Run batched External Source first
  • Use actual batch size from batched ES in per sample ES
• Affected modules and functionalities:
  • pyhon: Pipeline, ExternalSource
• Key points relevant for the review:
  • N/A
• Validation and testing:
  • Python unit tests
• Documentation (including examples):
  • N/A

JIRA TASK: N/A

[dali-automaton]

CI MESSAGE: [3840108]: BUILD FAILED