[chore] Clarify .count for updowncounters guidance

[ChrsMark]

Fixes #2306

Changes

This PR tries to clarfiy the guidance regarding the usage of .count for UpDownCounters as it was described at #2306.

/cc @trask @lmolkova @braydonk

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[trask]

I've added this to Mon SIG meeting agenda just to confirm with more folks, thanks

Dismissing as we seem to have a bigger problem, @lmolkova found. Let's see what we can come up to improve this.

[ChrsMark]

@lmolkova @joaopgrassi @trask, should we then keep the guidance and make it more explicit with sth like all updowncounters SHOULD be named with .count instead of using pluralisation?

[lmolkova]

@ChrsMark we have a bunch of metrics that use .active or some more suitable alternative to .count, so I was thinking about

- Use count instead of pluralization for UpDownCounters
+ Do not pluralize UpDownCounter names

with some examples using .count and others and explanation that it's a matter of consistency across conventions.

[ChrsMark]

@ChrsMark we have a bunch of metrics that use .active or some more suitable alternative to .count, so I was thinking about

- Use count instead of pluralization for UpDownCounters
+ Do not pluralize UpDownCounter names

with some examples using .count and others and explanation that it's a matter of consistency across conventions.

Ok, I'm fine with that. I updated the PR accordingly. If there are suggestions about the wording or more examples to add let me know.

[ChrsMark]

Thank's @lmolkova , your comments should be addressed now, please take another look.

[joaopgrassi]

@ChrsMark I think all comments are solved now, so I resolved them. I think we are good to merge this now. CC @lmolkova