misc(build): normalize sample-report build naming

[paulirish]

currently based off PR #12815

stemming from this thread #12815 (comment)

• build-dist-reports => build-sample-reports
  • no strong feelings. seems good and lines up with samplev2 which makes sense
• build-report-for-autodeployment.js ⟶ build/build-sample-reports.js
  • rename and relocation. feels good. i use this locally to test report stuff (so its not just about the autodeployment for me)
• now-build -> vercel-build
  • the vercel deployments rely on this convention. we could tell vercel to use a custom build command in their UI, but i kinda prefer continuing to use the convention. seems like they've been supporting the now- name, but might as well update it

tag #12879 as its slightly related.

[connorjclark]

LGTM (but land as separate commit)