Add support to variable sequences and file based configuration

[fbeltrao]

Purpose

• Allow defining a variable that is created out of a sequence of values
• Allow defining the configuration in file

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

[TechPreacher]

Looks great, thanks!!!

[gukoff]

Approved 🐛

side note

We could further support variables referencing to each other, with only one rule: variable is allowed to reference any variable declared before it.

All it takes is to replace strings by TelemetryTemplates in variable values on startup. And when generating values, evaluate these templates to strings.

Whether these super capabilities would help any of our users, I don't know 🙃

But one could do wild things like:

[
    {
      "name": "Counter"
    },
    {
      "name": "DeviceName",
      "random": true,
      "values": [ "Alice", "Bob" ]
    },
    {
      "name": "DeviceLength",
      "sequence": true,
      "values": [ "$.Counter", "$.Counter", "$.Counter", "$.Counter", "$.Counter", "true", "false", "$.Counter" ]
    },
    {
      "name": "DeviceLengthWithCmSuffix",
      "value": "$DeviceLength cm"
    },
    {
      "name": "DeviceDescription",
      "random": true,
      "value": ["$DeviceName of length $DeviceLengthWithCmSuffix", "$DeviceName:$DeviceLength"]
    }
  ]

[gukoff]

I approve, but in the future I'd limit ResetNotUsedReferencedVariables to a particular variable type that needs it:
#36 (comment)

[TechPreacher]

Still looks good to me :)