This makes it easier to view prometheus metrics.
Added a test case which demonstrates the new behavior - the test
initially failed as the output was ordered in the same order
as the fields were declared in the struct (i.e. foo_a, bar_a, foo_b,
bar_b). For that reason, I also had to change an existing test case
to sort the fields in the new expected order.
Signed-off-by: Hasnain Lakhani <m.hasnain.lakhani@gmail.com>
8fe04b035c