Check if image component is used

[jvarho]

The past couple of versions of Next.js have an indication of whether the image component is imported in .next/export-marker.json so use it to avoid building image handler when not used.

Should prevent issues like #1030 for people upgrading with a restricted role.

[codecov]

Codecov Report

Merging #1065 (9d9de4d) into master (64a5a60) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1065      +/-   ##
==========================================
+ Coverage   83.17%   83.19%   +0.02%     
==========================================
  Files          74       74              
  Lines        3049     3053       +4     
  Branches      864      867       +3     
==========================================
+ Hits         2536     2540       +4     
  Misses        460      460              
  Partials       53       53              

Impacted Files	Coverage Δ
packages/libs/lambda-at-edge/src/build.ts	95.73% <100.00%> (+0.04%)	⬆️

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[dphang]

Woops, looks like too many workflows were run at the same time, so we hit the GitHub API rate limit. Will try the workflow again after a few hours.