VGW Add-on has several resources that are not auto named

[brsteel]

Benefit/Result/Outcome

providing the hub vnet resource ID should provide in the input necessary to name all resources used in the add on.
This reduces the parameters required to run the add-on significantly.

Description

New resources created that do not have derivied names are, therefore they have to be manually given as parameters:
vgwname: <example: mlz-vgw-hub-dev-va>
pip names (2 of them): <example: mlz-pip-vgw-hub-dev-va-1>
lng name: <example: mlz-lng-hub-dev-va>
vgw route table name: <example: mlz-vgw-rt-hub-dev-va>

Resources required in parameters that are existing, but can probably be "discovered" or "assumed":
azure firewall name
hub vnet route table name
allowedazureaddressprefixes (should be derived from the vnetresourceidlist)
vgwlocation should match the resource group location of the hub virtual network resource group

Acceptance Criteria

the only parameters that need to be provided to the addon should be:

hubvirtualnetworkresourceid
vnetresourceidlist (spoke vnets participating in the vpn gateway access)
usesharedkey
sharedkey value (should be excluded from the actual parameters file so a prompt occurs at deployment time)
localaddressprefixes (on-prem subnets on the other side of the vpn gateway)
localgatewayipaddress