Update configuring resource guide per latest changes

[turkenh]

What happened?

There are couple of changes in Terrajet configuration interface that happened after the Configuring a resource guide is introduced first time.

We need to update the guide accordingly.

There are a couple of review comments in https://github.com/crossplane-contrib/terrajet/pull/130 which we would need to tackle first:

• https://github.com/crossplane-contrib/terrajet/pull/130#discussion_r749507600
• https://github.com/crossplane-contrib/terrajet/pull/130#discussion_r749508451
• https://github.com/crossplane-contrib/terrajet/pull/130#discussion_r752947141
• https://github.com/crossplane-contrib/terrajet/pull/130#discussion_r752947828
• https://github.com/crossplane-contrib/terrajet/pull/130#discussion_r749516661

How can we reproduce it?

Reflect latest changes to the guide.

[muvaf]

Just dropping note, we should add instructions about this ability https://github.com/crossplane-contrib/provider-jet-azure/issues/110