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 ⚠️

Additional details and impacted files

@@            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	Coverage Δ
internal/cbor_gen.go	37.08% <58.97%> (+6.16%)	⬆️