fix(package-rules): respect each dep update's fetchChangeLogs value

[justfalter]

Changes

Ensures that changelog fetching respects each dep update's specific fetchChangeLogs value.

Given the following renovate configuration: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/blob/fb9e070d0f9a4d6fc742c4a22edee2c9b055fece/.github/renovate.json5#L42-L61

  "packageRules": [
    {
      "matchPackageNames": [
        "lodash"
      ],
      "prBodyNotes": [
        "* lodash - should have no changelogs"
      ],
      "fetchChangeLogs": "off"
    },
    {
      // PROBLEM: the grouping of "lodash" with chalk and tar causes its fetchChangeLogs to not be respected
      "matchPackageNames": [
        "lodash",
        "chalk",
        "tar"
      ],
      "groupName": "group of unrelated packages"
    }
  ]

My expectation is that Renovate would never fetch changelogs for lodash. However, when grouped together with chalk and tar under group of unrelated packages, we find that renovate fetches changelogs for all packages, including lodash.

Before this change (lodash logs fetched):

• Run: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/actions/runs/24480887343/job/71544876893
• (wrong) lodash, tar, and chalk all have changelogs: Update group of unrelated packages justfalter/renovate-test-packagerules-fetchchangelogs#9

After this change, the PR created by renovate only contains changelogs for chalk and tar, but not lodash:

• Run: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/actions/runs/24481738609/job/71547632550
• (expected) lodash does not have changelogs, but tar and chalk have changelogs: Update group of unrelated packages justfalter/renovate-test-packagerules-fetchchangelogs#10

---

We can further explore the effectiveness of the change with a more elaborate configuration, where the top-level has fetchChangeLogs: off: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/blob/0ea69c18b9171e38c56440c762faa68109d3d0d5/.github/renovate.json5#L41-L95

  "fetchChangeLogs": "off",
  "packageRules": [
    {
      "matchPackageNames": [
        "typescript"
      ],
      "prBodyNotes": [
        "* typescript - inherits fetchChangeLogs from base config"
      ],
    },
    {
      "matchPackageNames": [
        "grunt"
      ],
      "prBodyNotes": [
        "* grunt - fetches change logs"
      ],
      "fetchChangeLogs": "pr"
    },
    {
      "matchPackageNames": [
        "chalk"
      ],
      "prBodyNotes": [
        "* chalk - should have changelogs"
      ],
      "fetchChangeLogs": "pr"
    },
    {
      "matchPackageNames": [
        "tar"
      ],
      "prBodyNotes": [
        "* tar - should have changelogs"
      ],
      "fetchChangeLogs": "pr"
    },
    {
      "matchPackageNames": [
        "lodash"
      ],
      "prBodyNotes": [
        "* lodash - should have no changelogs"
      ],
      "fetchChangeLogs": "off"
    },
    {
      // PROBLEM: the grouping of "lodash" with chalk and tar causes its fetchChangeLogs to not be respected
      "matchPackageNames": [
        "lodash",
        "chalk",
        "tar"
      ],
      "groupName": "group of unrelated packages"
    }

Before the change:

• Run: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/actions/runs/24482213234/job/71549162174
• (wrong) lodash, tar, and chalk all have changelogs: Update group of unrelated packages justfalter/renovate-test-packagerules-fetchchangelogs#15
• (expected) typescript (inherited off) does not have changelogs: Update dependency typescript to v6 justfalter/renovate-test-packagerules-fetchchangelogs#17
• (expected) grunt (overridden pr) has changelogs: Update dependency grunt to v1.6.2 justfalter/renovate-test-packagerules-fetchchangelogs#13

After the change::

• Run: https://github.com/justfalter/renovate-test-packagerules-fetchchangelogs/actions/runs/24482561172/job/71550255278
• (expected) lodash does not have changelogs, but tar and chalk have changelogs: Update group of unrelated packages justfalter/renovate-test-packagerules-fetchchangelogs#22
• (expected) typescript (inherited off) does not have changelogs: Update dependency typescript to v6 justfalter/renovate-test-packagerules-fetchchangelogs#24
• (expected) grunt (overridden pr) has changelogs: Update dependency grunt to v1.6.2 justfalter/renovate-test-packagerules-fetchchangelogs#20

Portions of this PR previously appeared in #42368

Context

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• This closes an existing Issue, Closes: #
• This doesn't close an Issue, but I accept the risk that this PR may be closed if maintainers disagree with its opening or implementation

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The public repository:

[justfalter]

It felt cleaner to just create a new pull request --- I believe that I've addressed all the feedback provided in #42368 (including request viceice's request for some more elaborate testing).

[justfalter]

I agree with viceice's comment from from my old PR that an upgrade will probably always have fetchChangeLogs set, but the underlying types have them as optional. I feel like this resolve function is a good compromise for avoiding having to delve deep into renovate's types.