Make kvp's Debug impls a lot more readable

[nightkr]

Description

Changes the output from:

Labels(
    KeyValuePairs(
        {
            KeyValuePair {
                key: Key {
                    prefix: None,
                    name: KeyName(
                        "group",
                    ),
                },
                value: LabelValue(
                    "default",
                ),
            },
            KeyValuePair {
                key: Key {
                    prefix: None,
                    name: KeyName(
                        "role",
                    ),
                },
                value: LabelValue(
                    "namenode",
                ),
            },
            KeyValuePair {
                key: Key {
                    prefix: Some(
                        KeyPrefix(
                            "app.kubernetes.io",
                        ),
                    ),
                    name: KeyName(
                        "component",
                    ),
                },
                value: LabelValue(
                    "namenode",
                ),
            },
            KeyValuePair {
                key: Key {
                    prefix: Some(
                        KeyPrefix(
                            "app.kubernetes.io",
                        ),
                    ),
                    name: KeyName(
                        "instance",
                    ),
                },
                value: LabelValue(
                    "simple-hdfs",
                ),
            },
            KeyValuePair {
                key: Key {
                    prefix: Some(
                        KeyPrefix(
                            "app.kubernetes.io",
                        ),
                    ),
                    name: KeyName(
                        "name",
                    ),
                },
                value: LabelValue(
                    "hdfs",
                ),
            },
            KeyValuePair {
                key: Key {
                    prefix: Some(
                        KeyPrefix(
                            "app.kubernetes.io",
                        ),
                    ),
                    name: KeyName(
                        "role-group",
                    ),
                },
                value: LabelValue(
                    "default",
                ),
            },
        },
    ),
)

To:

Labels(
    KeyValuePairs(
        {
            "group": "default",
            "role": "namenode",
            "app.kubernetes.io"/"component": "namenode",
            "app.kubernetes.io"/"instance": "simple-hdfs",
            "app.kubernetes.io"/"name": "hdfs",
            "app.kubernetes.io"/"role-group": "default",
        },
    ),
)

The useful information is still there, it's just.. a lot more readable if we cut away the fluff.

Definition of Done Checklist

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Author

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1. Changes are OpenShift compatible
2. CRD changes approved
3. Integration tests passed (for non trivial changes)

Reviewer

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1. Code contains useful comments
2. (Integration-)Test cases added
3. Documentation added or updated
4. Changelog updated
5. Cargo.toml only contains references to git tags (not specific commits or branches)

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1. Feature Tracker has been updated
2. Proper release label has been added