1. Paginate through all current level blocks before recursing into
children (before this PR we would go back and forth between paginate and
recurse)
2. For top-level blocks only, split blocks into 5 lists, and
concurrently get their content
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From my local timing benchmarks, this speeds up the tool call by ~60%
(23 seconds to 9.1 seconds) for larger Notion pages
Without optimization: Avg 22995
Attempt 1: 27503.49497795105
Attempt 2: 20863.977909088135
Attempt 3: 20888.309955596924
Attempt 4: 18574.61714744568
Attempt 5: 27147.75586128235
With optimization: Avg 9148.6
Attempt 1: 9941.372871398926
Attempt 2: 10097.685098648071
Attempt 3: 7855.895042419434
Attempt 4: 9078.719854354858
Attempt 5: 8772.69196510315
8f87212058