VM Copy support

[Didainius]

This PR adds support for "VM Copy" operation. This allows users to create VMs from from existing VMs. This works by adding copy_from_vm_id in vcd_vapp_vm and vcd_vm resources.

There is one caveat due to a known VCD bug - when creating a Standalone VM copy and source VM is in different VDC, - destination VM must have a sizing_policy_id specified, as otherwise it will return an error (this is also highlighted in docs)

Flow diagram for create functions of vcd_vapp_vm and vcd_vm (updated from PR #901 version to reflect latest changes)

• Purple shows the main flow of code for Create
• Green blocks signify API call definition for each of VM types that are being created.
• Yellow blocks signify where additional code can be hooked up for particular scope

flowchart TD
    S[VM Create]
    S ==> AAAA
    AAAA{Standanlone or vApp VM?}
    AAAA --> |resource vcd_vm| AA{vApp VM or Standalone}
    AAAA --> |resource vcd_vapp_vm| A{vApp VM or Standalone}

    AA[func resourceVcdStandaloneVmCreate] --> B[func genericResourceVmCreate]
    A[func resourceVcdVAppVmCreate] -->|lock parent vApp\n defer unlock| B[func genericResourceVmCreate]

    BB{Is template, empty, or VM Copy}

    B --> BB

    BB -->|"isVmFromTemplate || isVmCopy"| D[func createVmFromImage]
    D --> D3[func lookupSourceImage]
    D3 -->|"isVmFromTemplate"| D4[func lookupSourceCatalogTemplate]
    D3 -->|"isVmCopy"| D5[func lookupSourceVm]

    D4 --> D7[Source Image Identified]
    D5 --> D7

    BB -->|isEmptyVm| E[func createVmEmpty]

    DDD([vApp VM from template])
    DDDD(Standalone VM from template)
    

    EEE(Empty vApp VM)
    EEEE(Empty Standalone VM)

    DD([Optionally perform template VM specific actions])
    EE([Optionally perform empty VM specific actions])


   DDOPTIONAL1([Optionally perform vApp VM template specific actions])
   DDOPTIONAL2([Optionally perform Standalone VM template specific actions])

   EEOPTIONAL1([Optionally perform Empty vApp VM specific actions])
   EEOPTIONAL2([Optionally perform Empty Standalone VM specific actions])


    D7 --> |Is vApp VM| DDD
    D7 --> |Is Standalone VM| DDDD

    E --> |Is vApp VM| EEE
    E --> |Is Standalone VM| EEEE

    DDD --> DDOPTIONAL1
    DDOPTIONAL1 --> DD
    DDDD --> DDOPTIONAL2
    DDOPTIONAL2 --> DD

    EEE --> EEOPTIONAL1
    EEOPTIONAL1 --> EE
    EEEE --> EEOPTIONAL2
    EEOPTIONAL2 --> EE


    F[func genericResourceVmCreate \n'Common API calls for ALL VMs' ]
    DD --> F
    EE --> F


    F ==> G
    G ==> Z
    
    G[func genericResourceVmCreate\nlast step -> power on]

    Z[VM Created]

style DDD fill:#45f248,stroke:#333,stroke-width:4px
style DDDD fill:#45f248,stroke:#333,stroke-width:4px
style EEE fill:#45f248,stroke:#333,stroke-width:4px
style EEEE fill:#45f248,stroke:#333,stroke-width:4px


style F fill:#F1EE8E,stroke:#333,stroke-width:4px
style DD fill:#F1EE8E,stroke:#333,stroke-width:4px
style EE fill:#F1EE8E,stroke:#333,stroke-width:4px
style DDOPTIONAL1 fill:#F1EE8E,stroke:#333,stroke-width:4px
style DDOPTIONAL2 fill:#F1EE8E,stroke:#333,stroke-width:4px

style EEOPTIONAL1 fill:#F1EE8E,stroke:#333,stroke-width:4px
style EEOPTIONAL2 fill:#F1EE8E,stroke:#333,stroke-width:4px

Closes #562

Acceptance tests passed in 10.4.0 and 10.5.1

[lvirbalas]

This is great! Just a few suggestions inline.

[adambarreiro]

LGTM!