[tfswitch-parity] Support version ranges defined in terragrunt.hcl

[kvendingoldo]

Describe the solution you'd like
Please replicate this feature from tfswitch. https://tfswitch.warrensbox.com/Quick-Start/#use-terragrunthcl-file

Additional context
It's backport of the original issue from tofuenv: tofuutils/tofuenv#33
cc @skyzyx

[dvaumoron]

Does not seem complicated to do (there is already hcl parsing for .tf files), what should be the prioritiy order ? I suggest forcing env var , then version files (.opentofu-version or .terraform-version), then terragrunt.hcl file, and last scanning for .tf files

I want to underline that if we continue to add support for more ways to choose a version to use, the priority rules should be clearly indicated by the documentation.

[dvaumoron]

Change done, however the code in semantic.go is not very readable, i will think about a way to refactor it.

[dvaumoron]

I think that's better. Any remark ?

[kvendingoldo]

@dvaumoron I think so! Great!