Create Consolidated output

[tfhartmann]

In #73 the topic of outputs came up - #73 (comment) . A feature add to consolidate the outputs (subnets_names, subnets_ips, subnets_regions, subnets_private_access, subnets_flow_logs, subnets_secondary_ranges) into a map indexed by subnet name was proposed.

I'm creating this issue to track that conversation and works.

I propose that a new output be created without removing the old outputs so as not introduce a breaking change to this module