Improve NKG installation experience

[pleshakov]

Is your feature request related to a problem? Please describe.

• too many manifests files in https://github.com/nginxinc/nginx-kubernetes-gateway/tree/main/deploy/manifests , which complicates installation process
• no uninstallation instructions

Describe the solution you'd like

• consolidate files into something like quickstart.yaml that contains all the k8s manifests for the static-mode install.
• add uninstallation instructions

Describe alternatives you've considered
none

Additional context
none

[mpstefan]

Split into #780 and #781, slated for 0.6