Allow dependent mods to have the same variable name as the parent mod (the parent mod variable will win)

[kaidaguerre]

MacBook-Pro:morejunk jsmyth$ steampipe mod list

local
├── github.com/turbot/steampipe-mod-aws-tags@v0.3
└── github.com/turbot/steampipe-mod-azure-tags@v0.3

MacBook-Pro:morejunk jsmyth$ 
MacBook-Pro:morejunk jsmyth$ 
MacBook-Pro:morejunk jsmyth$ 
MacBook-Pro:morejunk jsmyth$ steampipe query
Error: failed to load workspace: Failed to decode all mod hcl files
Mod defines more than one resource named 'aws_tags.var.tag_limit'
(/Users/jsmyth/src/junk/morejunk/.steampipe/mods/github.com/turbot/steampipe-mod-aws-tags@v0.3/controls/limit.sp:1,1-21)
Mod defines more than one resource named 'aws_tags.var.mandatory_tags'
(/Users/jsmyth/src/junk/morejunk/.steampipe/mods/github.com/turbot/steampipe-mod-aws-tags@v0.3/controls/mandatory.sp:1,1-26)
Mod defines more than one resource named 'aws_tags.var.prohibited_tags'
(/Users/jsmyth/src/junk/morejunk/.steampipe/mods/github.com/turbot/steampipe-mod-aws-tags@v0.3/controls/prohibited.sp:1,1-27)
MacBook-Pro:morejunk jsmyth$ 

2 parts to this:

1. add intelligence to the variable validation to ignore errors from duplicate variables in depdency mods
2. add scoping when setting variable values to allow setting of variables values in dependency mods

2 needs design thought/input