Use ind_jsonb type class directly for ApplicationSetting

What does this MR do and why?

This is a work around for fixing the memory cache for ApplicationSetting during code reloads. I'm not sure who holds the reference to the unloaded type, but this seems to work for now. 😅

How to set up and validate locally

On master open a rails console, wait for it to load and execute a reload! command. This is the error that will show and crash the process:

TypeError: Gitlab::Database::Type::IndifferentJsonb can't be referred to
from /Users/marius/.gem/ruby/2.7.5/gems/activesupport-6.1.6.1/lib/active_support/cache.rb:841:in `dump'
[2] pry(main)>

this points to

      # Duplicates the value in a class. This is used by cache implementations that don't natively
      # serialize entries to protect against accidental cache modifications.
      def dup_value!
        if @value && !compressed? && !(@value.is_a?(Numeric) || @value == true || @value == false)
          if @value.is_a?(String)
            @value = @value.dup
          else
            @value = Marshal.load(Marshal.dump(@value))
          end
        end
      end

Here we're trying to dump an ApplicationSetting instance with an instance of the Type class that doesn't exist anymore.

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Related to #383153 (closed)