Fix: Block stream ignoring configured endBlock in specific cases

[dimitrovmaksim]

Fixes two issues that caused subgraphs to scan blocks well beyond their configured endBlock.

1. Block-skip optimization bypasses max_end_block check when block has no triggers, which causes the block stream to scan for blocks beyond the max end block until another condition is met.
2. An edge case where max_end_block is set to None when multiple data sources share the same endBlock. max_end_block was computed by comparing data_sources.len() with end_blocks.len(), but end_blocks is a BTreeSet, which removes duplicated values, resulting in data_sources and end_blocks legths to not be equal in this case.

[lutter]

Nice!