add a flag for poll interval

[d-honeybadger]

Description of your changes

Adds a flag for poll interval and changes poll default from 1 to 10 min (current upjet's default as per https://github.com/upbound/upjet/blob/main/docs/sizing-guide.md)

I have:

• [x] Read and followed Crossplane's contribution process.
• [ ] Run make reviewable test to ensure this PR is ready for review.

How has this code been tested