chore(runtime): reorder metrics to be grouped by cfg-gates

[jlizen]

Motivation

#7449 fixed the generated cfg gates in our rustdocs for runtime metrics. In the interest of reviewability, we avoided reordering the metric methods.

However this resulted in interwoven groups of cfg-gates and multiple macro declarations per each. This hurts maintainability and readability.

Solution

I reorganized the module to group all like-gated methods together.

[ADD-SP]

It would be better splitting a huge commit into serval commit, one method, one commit. This could make the code review easier.