add rule: terraform_module_version

[bendrucker]

Adds a terraform_module_version rule that Terraform modules from the registry should set a source. Similar to terraform_module_pinned_source, this is enabled by default.

Users can optionally specify exact = true to require that version be an exact 3 part version.

This brings back some Terraform files in addrs as well as dependent packages. They were necessary to determine whether a source resolves to a registry:

https://github.com/hashicorp/terraform/blob/120629848761f5434c75b9876a030f8145abf043/internal/addrs/module_source.go#L63-L73

This could also be useful for terraform-linters/tflint-ruleset-terraform#18 which would want to check whether a source is a local one before applying some rules to it.

Fixes #1176

[bendrucker]

Whoops, tagged the wrong # above

[wata727]

I'm a little worried if this regex is enough. For instance, go-version uses the following regexp:
https://github.com/hashicorp/go-version/blob/v1.3.0/version.go#L18-L31

Ideally, it would be nice to be able to verify that the f in the Constraint is the constraintEqual, but this struct doesn't seem to expose the logic...
https://github.com/hashicorp/go-version/blob/v1.3.0/constraint.go#L30-L31

[bendrucker]

Agree. Spent a bunch of time looking at constraints and saw that the constraint type was not exposed. Was thinking of this more complicated regexp compilation:

https://github.com/hashicorp/go-version/blob/c2de2312d363381e4254abec260c6df2b1226483/constraint.go#L45-L49

But the version one is easy to reuse.

[bendrucker]

After trying this, the go-version regex doesn't require major/minor/patch and the test ensuring 1.0 is rejected as exact fails. Grabbed a regex from the semver.org docs and added a test ensuring that prerelease suffixes work.

[bendrucker]

Revised per your comments, ready for another look

[wata727]

👍