Fix websocket subscription performance issue

[chenyukang]

What problem does this PR solve?

Fixes #4489

The current channel size is too small, which may introduce RecvError::Lagged when the workload is high.

What is changed and how it works?

What's Changed:

• enlarge the notify channel size, keep it same with ckb_notify::NOTIFY_CHANNEL_SIZE.
• ignore the RecvError::Lagged and continue to get the later notifications.

Related changes

• PR to update owner/repo:
• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code ci-runs-only: [ quick_checks,linters ]

Side effects

• Performance regression
• Breaking backward compatibility

Release note

Title Only: Include only the PR title in the release note.