Add gomplate gsutil exiftool updates for CNG

It adds:

• gomplate
• exiftool
• gsutil

Related to: https://gitlab.com/gitlab-org/build/CNG/-/issues/2058

A preview (I turned off package rule): lucus.li/CNG#1

Equivalent renovate.json:

{
    "$schema": "https://docs.renovatebot.com/renovate-schema.json",
    "extends": [
        "config:base"
    ],
    "enabledManagers": [
        "custom.regex"
    ],
    "packageRules": [
        {
            "matchPackageNames": [
                "hairyhenderson/gomplate"
            ],
            "matchManagers": [
                "custom.regex"
            ],
            "allowedVersions": "<4.0.0"
        }
    ],
    "customManagers": [
        {
            "customType": "regex",
            "fileMatch": [
                "^gitlab-toolbox/Dockerfile$",
                "^gitlab-toolbox/Dockerfile.build.ubi$"
            ],
            "matchStrings": [
                "GSUTIL_VERSION=\"?(?<currentValue>[^\"\\s]+)\"?"
            ],
            "depNameTemplate": "GoogleCloudPlatform/gsutil",
            "datasourceTemplate": "github-tags",
            "extractVersionTemplate": "^v?(?<version>.*)$"
        },
        {
            "customType": "regex",
            "fileMatch": [
                "^gitlab-exiftool/Dockerfile$",
                "^gitlab-exiftool/Dockerfile.build.ubi$"
            ],
            "matchStrings": [
                "EXIFTOOL_VERSION=\"?(?<currentValue>[^\"\\s]+)\"?"
            ],
            "depNameTemplate": "exiftool/exiftool",
            "datasourceTemplate": "github-tags"
        },
        {
            "customType": "regex",
            "fileMatch": [
                "^gitlab-gomplate/Dockerfile$",
                "^gitlab-gomplate/Dockerfile.build.ubi$",
                "^ci_files/variables.yml$"
            ],
            "matchStrings": [
                "GOMPLATE_VERSION=\"?v(?<currentValue>[^\"\\s]+)\"?",
                "GOMPLATE_VERSION: \"v(?<currentValue>\\S+)\""
            ],
            "depNameTemplate": "hairyhenderson/gomplate",
            "datasourceTemplate": "github-tags",
            "extractVersionTemplate": "^v?(?<version>.*)$"
        }
    ]
}