Housekeeper: Add support for `ci.skip`

What does this MR do and why?

In certain scenarios, when creating a Merge Request (MR) through a Keep, it's beneficial to bypass the pipeline creation upon committing changes. This is handy in cases where a keep can commit files in an automated fashion, yet some files might require manual updates from the user, such as specs. In such cases, before the manual updates to specs are made, the pipeline is gonna fail anyway, and it is better to skip it rather than needlessly running the pipeline.

By providing an option within the keep to skip the pipeline during commit creation using GitLab's push options, specifically -o ci.skip, we can prevent the pipeline from running needlessly, if need be. This option is turned off by default, and needs to be turned on from within a keep.

Usage

# keeps/pretty_useless_keep.rb

module Keeps
  class PrettyUselessKeep < ::Gitlab::Housekeeper::Keep
    def each_change
      (1..3).each do |i|
        file_name = "new_file#{i}.txt"

        `touch #{file_name}`

        change = ::Gitlab::Housekeeper::Change.new

        change.identifiers = [self.class.name.demodulize, "new_file#{i}"]

        change.title = "Make new file #{file_name}"

        change.description = <<~MARKDOWN
        ## New files

        This MR makes a new file #{file_name}
        MARKDOWN

        change.labels = %w(type::feature)

        change.changed_files = [file_name]

        change.push_options.ci_skip = true # <==== PUSH OPTIONS CAN BE SPECIFIED THIS WAY

        yield(change)
      end
    end
  end
end

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