Add option to disable Tunable Validation

# Enhancement Request: Remove Tunables Validation

## Summary

[Provide a brief, high-level overview of the proposed enhancement. What is it, and what problem does it solve?]

Currently there is a list of allowable tunables a user can try to run dfdl extension at constants/tunables.json. Only tunables that are on this list will be allowed to saved and ran by the extension. If a new daffodil version is released with a new tunable and the constant list in the extension was not updated to match daffodil, a user trying to use the extension would be met with failure, even though it is a valid tunable.

For example, above is the list of allowed tunables. If a new valid tunable was added to a later version of Daffodil and this list is not updated, that valid tunable would not work.

## Proposed Solution / Description

A minimal solution that would allow a user to bypass validation would be adding a switch to the launch.json. For example validate_tunables = true. This would default to true in the backend and would not be included in the launch.json by default. A user would have to and add validate_tunables = false, and then all validation on tunables would stop. With this option a less aware user would not accidental add this to the launch config, and it gives a way to bypass our list without adding complexity overall.

There are other solutions but this seemed to be the most efficient way to do this

### Addtional Notes
[
- **New Feature:** ...
- **Improved Workflow:** ...
- **Technical Changes:** ...

]

Start with constants/tunables.json and trace the backend validation path, then inspect how launch.json options are read. Add the proposed validate_tunables setting with validation enabled by default, and verify that setting it to false permits tunables outside the maintained list.

Written by the indexing model from the issue text.