Docs: Add full bootstrap delete and reentry modes as well as LZ delete - assist development and bootstrap triage

Both the bootstrap docs and script
https://github.com/ssc-spc-ccoe-cei/gcp-tools/blob/main/scripts/bootstrap/setup-kcc.sh#L75

and the core landing zone - need automated deletion sections to fully remove the LZ and the KCC cluster and any SA's and IAM permissions added.

This will assist repeated development and bootstrap triage

TODO: fix the numbering in https://github.com/GoogleCloudPlatform/pubsec-declarative-toolkit/blob/main/docs/landing-zone-v2/README.md#2b-deploy-the-infrastructure-using-kpt
- see package and kcc cluster deletion in #344