fix: split bitswap messages

[achingbrain]

Split large bitswap messages into multiple smaller messages to keep them under the max message size other implementations will accept.

Change checklist

• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation if necessary (this includes comments as well)
• [x] I have added tests that prove my fix is effective or that my feature works