Execute hooks in series as per pre-v10 releases

[benlancaster]

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Since v10, the functions provided to afterCopy, afterExtract and afterPrune no longer execute in series. In some cases, this behaviour is desirable since one hook may effect changes that another hook assumes have already happened. I couldn't see anything about this change in the release notes, so this PR restores that behaviour whilst still using Promises internally.

If this change is welcome, could someone please give me some pointers getting the unit tests passing? I'm having a hard time, either seeing intermittent failures on the sequential ordering assertions (presumably because the packagerTest builds two packages), or the following:

  platform=all test (one arch) (afterPrune hook)

  Rejected promise returned by test. Reason:

  Error {
    cmd: 'npm prune --production',
    code: 1,
    killed: false,
    signal: null,
    message: `Command failed: npm prune --production␊
    npm WARN @4.99.101 No description␊
    npm WARN @4.99.101 No repository field.␊
    npm WARN @4.99.101 No license field.␊
    ␊
    npm ERR! May not delete: /private/var/folders/nz/s1gw0mtj4jq8jqc7w2p090tr0000gn/T/75089d8c4e4d0acbb0bcbe90f07b7de5/electron-packager/linux-ia32/packagerTest-linux-ia32/resources/app/node_modules/.bin␊
    ␊
    npm ERR! A complete log of this run can be found in:␊
    npm ERR!     /Users/username/.npm/_logs/2018-03-16T16_58_32_665Z-debug.log␊
    `,
  }

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[benlancaster]

What's the right way to do this without the spread operator?

[benlancaster]

In fact it looks like Node 4 will be EOL at the end of April, so I guess this could stay in if this gets accepted and released after that

[malept]

I appreciate the effort you made in this PR, however, I'm unlikely to revert the feature change to the hooks. As a counterproposal, I've written #814, which I hope addresses your concerns.

[benlancaster]

Yeah that's great, thank you.