Fix logging handling for API integer params

What does this MR do?

When encoding the values to be logged with lograge we handled all cases except Integer, which means legit int parameters being sent to the API would be logged as null, this adds encoding for integer parameters as well.

Related to #273663 (closed)

Screenshots (strongly suggested)

Before:

irb(main):001:0> Gitlab::GrapeLogging::Formatters::LogrageWithTimestamp.new.send(:process_params, {"params": {"test1": 123, "test2": "123"}})
=> [{:key=>:test1, :value=>nil}, {:key=>:test2, :value=>"123"}]

After:

irb(main):001:0> Gitlab::GrapeLogging::Formatters::LogrageWithTimestamp.new.send(:process_params, {"params": {"test1": 123, "test2": "123"}})
=> [{:key=>:test1, :value=>"123"}, {:key=>:test2, :value=>"123"}]

Does this MR meet the acceptance criteria?

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