refactor scraper in azuremonitorreceiver

[nslaughter]

Component(s)

receiver/azuremonitor

Describe the issue you're reporting

The azuremonitorreceiver scraper needs refactoring to clarify code, which will allow us to address bugs with zero-values sometimes as reported in #34265.

[github-actions]

Pinging code owners for receiver/azuremonitor: @nslaughter @codeboten. See Adding Labels via Comments if you do not have permissions to add labels yourself.

[crobert-1]

Issue was filed by a code owner and makes sense to me, removing needs triage.