Improve custom Renovate presets and config

[robo9k]

Also see robo9k/rust-magic-sys#155

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Currently all crate updates are "fix(deps)" as semantic commit type
However when only the Cargo.lock is updated, this could be "chore(deps)" as those do not directly influence our users and thus should be handled differently e.g. in CHANGELOG / by release-plz

Example for #393 from https://developer.mend.io/github/robo9k/rust-magic/-/job/9a37821e-7b3f-4e9b-bd14-b1788b10b81c

          {
            "currentValue": "2.5.0",
            "currentVersion": "2.5.0",
            "datasource": "crate",
            "depName": "bitflags",
            "depType": "dependencies",
            "fixedVersion": "2.5.0",
            "isSingleVersion": true,
            "lockedVersion": "2.5.0",
            "managerData": {
              "nestedVersion": false
            },
            "packageName": "bitflags",
            "versioning": "cargo",
            "updates": [
              {
                "bucket": "non-major",
                "newVersion": "2.9.4",
                "newValue": "2.5.0",
                "newMajor": 2,
                "newMinor": 9,
                "newPatch": 4,
                "updateType": "minor",
                "isBreaking": false,
                "isLockfileUpdate": true,
              }
            ]
          },