module.calls: Report requirements and installed versions separately

[radeksimko]

Background

Currently module.calls reports only details about installed modules based on the module manifest.

#987 is expected to change behaviour of that command where it will report modules declared in the configuration instead. version field is also expected to become version constraint, which will match the original (previously wrong) docs: https://github.com/hashicorp/terraform-ls/blob/main/docs/commands.md#modulecalls

Clients would however benefit from having details about both required modules and installed ones.

Also we should continue reporting accurate docs links which point to the particular version of module installed, not the latest version.

Proposal

• follow the structure of module.providers which already reports both constraints and installed providers
• introduce v2 of module.calls which will include declared_modules and installed_modules with appropriate details