Update deps, re-generate cbor-gen output, add dependabot

[rvagg]

Full dependencies update in here, which included a minor break in the blockstore api so our internal mock needed context plumbing. cbor-gen has changed slightly since this but it's fairly minor and the diff is small enough to be grokked.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 58.97436% with 16 lines in your changes missing coverage. Please review.

Project coverage is 53.98%. Comparing base (ebb220a) to head (cb3a5e1).

Files	Patch %	Lines
internal/cbor_gen.go	58.97%	5 Missing and 11 partials :warning:

Additional details and impacted files

[](https://app.codecov.io/gh/filecoin-project/go-amt-ipld/pull/92?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=filecoin-project) ```diff @@ Coverage Diff @@ ## master #92 +/- ## ========================================== + Coverage 53.32% 53.98% +0.66% ========================================== Files 13 13 Lines 1324 1343 +19 ========================================== + Hits 706 725 +19 Misses 465 465 Partials 153 153 ``` | [Files](https://app.codecov.io/gh/filecoin-project/go-amt-ipld/pull/92?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=filecoin-project) | Coverage Δ | | |---|---|---| | [internal/cbor\_gen.go](https://app.codecov.io/gh/filecoin-project/go-amt-ipld/pull/92?src=pr&el=tree&filepath=internal%2Fcbor_gen.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=filecoin-project#diff-aW50ZXJuYWwvY2Jvcl9nZW4uZ28=) | `37.08% <58.97%> (+6.16%)` | :arrow_up: |