[parent] filecoin/offer flow

[hannahhoward]

In the new world, clients themselves must implement filecoin/offer

• fix issues in capabilities and handlers for filecoin/offer #51
• infra for filecoin offer #52
• client work for filecoin offer #53

Next:

• filecoin-api storefront reads Blob bytes to derive Piece CID from anywhere w3up#1349

[vasco-santos]

See:

• feat: api waits for trigger filecoin pipeline from the client w3up#1332
• feat: upgrade storefront api with filecoin offer from bucket event instead of directly compute w3infra#343
• filecoin/offer from client rollout plan w3infra#344

[vasco-santos]

First PR was merged, second is now ready for review

[reidlw]

1 of 2 PR's merged, second one is in review. ETA tomorrow. @Gozala to do the PR review.