Add support for 'terraform show'

[brk3]

Example usage:

Show current state:

/tf/rover/rover.sh \
  -lz /tf/caf/landingzones/caf-terraform-landingzones/caf_solution/ \
  -level level3 \
  -tfstate aks.tfstate \
  -env foo \
  -a show [-json]

Show a plan file:

/tf/rover/rover.sh \
  -lz /tf/caf/landingzones/caf-terraform-landingzones/caf_solution/ \
  -level level3 \
  -tfstate aks.tfstate \
  -env foo \
  -a show [-json] /tmp/out.plan

Implements #181

[brk3]

Hi Rover team, I've had to modify scripts/tfstate_azurerm.sh:other() to not pass -state by default. Not all 'other' commands take this arg, show being one. However I'm concerned this may break certain commands falling through to the other function that may require the state file?

If someone has some of these use cases would appreciate if they could confirm this patch is OK for their use case.

[LaurentLesle]

Thanks @brk3 . Going to include it in the next rover release and do the integration test into the tfc branch

[arnaudlh]

thanks @brk3 for your contribution to Cloud Adoption Framework!

[arnaudlh]

Tested and will need more rework so rolled back @brk3 ! Lets iterate for next month release.