feat: add start_height support to FilterIter

[kafeelraza]

Description

Add start_height support to bitcoind_rpc::bip158::FilterIter::new.

This allows filter scanning to recover from deep reorgs by resuming from a configured starting height when no common ancestor is found above that height.

Notes to the reviewers

This PR:

• adds a start_height parameter to FilterIter
• updates recovery behavior for deep reorg handling
• adds/updates tests covering recovery from invalid checkpoints
• updates docs/comments describing the new behavior

Closes #2126

Changelog notice

Added start_height support to bitcoind_rpc::bip158::FilterIter::new to improve deep reorg recovery behavior.

Checklists

All Submissions:

• I followed the contribution guidelines

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

[kafeelraza]

Hi! I'd like to work on this issue.

This PR adds start_height support to bitcoind_rpc::FilterIter::new, similar to the existing behavior in Emitter::new, and also updates the related documentation.