chore: fix code coverage, drop ncp

[kjin]

• ncp causes issues with running scripts locally. It hasn't been updated in 4 years, so I'm dropping it favor of just cp -r cpy.
• We were writing coverage info to coverage but codecov appears to expect these files to exist in .coverage.
• I disabled --all as it slows down CI a ton, enough to cause flakes.
• I added CI Codecov flags. Not 100% sure if it will work until we can view diffs, but this would allow different coverage reports for different Node versions.

[ofrobots]

cp -r wouldn't work on windows.

[kjin]

@ofrobots ah, thanks for the reminder.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@98f95e3). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1013   +/-   ##
=========================================
  Coverage          ?   91.83%           
=========================================
  Files             ?      107           
  Lines             ?     6380           
  Branches          ?      485           
=========================================
  Hits              ?     5859           
  Misses            ?      382           
  Partials          ?      139

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[ofrobots]

For posterity, what are the problems that ncp is causing locally?

[kjin]

ncp has an issue where sometimes a callback isn't called. Since I promisify it that means a Promise won't resolve, and my build script never continues -- it just exits with error code 0 (which IMO is the worst part). AvianFlu/ncp#131 is an example, their issue list seems to suggest several such problems.

The repo and module seem unmaintained, so I don't have hope that this will be fixed.