exporter/loadbalancingexporter: make dns resolver interval and timeout configurable

[jvilhuber]

Is your feature request related to a problem? Please describe.
I frequently see these errors in my logs:

{"level":"warn","ts":1653102273.0902977,"caller":"[email protected]/resolver_dns.go:106","msg":"failed to resolve","kind":"exporter","name":"loadbalancing","resolver":"dns","error":"i/o timeout"}

Seems at times the cluster may just be slow and the default 1-second (every 5 seconds) timeout is too short.

Describe the solution you'd like
Make the dns lookup interval and timeout configurable.

Describe alternatives you've considered
No alternative comes to mind. Making the timeout longer across the board may make other environments unstable.

Additional context

[TylerHelmuth]

Seems like a good addition to the config. @jvilhuber is this something you plan to contribute?

[jvilhuber]

I can certainly give it a go! I'm currently waiting for my company to approve the CLA.

[jvilhuber]

This was recently fixed/merged.