feat: allow to show required by module version explicitly

[ikorchynskyi]

Proposed changes simplify the possibility to use tfswitch in automation: my own use-case is to fetch the required by project terraform version and to use specific version of docker image with terraform inside the CI/CD pipeline.

Related diagnostic messages has been moved to stderr to allow output to be fetched like

$ echo "Version required by module: $(go run main.go --chdir ~/foo/ --show-latest-required)"
Reading required version from terraform file
Reading required version from constraint: ~> 1.4.0, < 1.4.5
Matched version: 1.4.4
Version required by module: 1.4.4

[yermulnik]

Somewhat alike use case that I created issue two years ago for: https://github.com/warrensbox/terraform-switcher/issues/154

[ikorchynskyi]

1. This feature might probably need to be reflected in README
2. New cmdline arg should be covered with test(s) if possible please
3. This works oddly on my end:

But seems any "--show-*" flag works in a same way when there is a .toml file provided

	case fileExists(TOMLConfigFile) || fileExists(HomeTOMLConfigFile):

in that case there is no --show flag check at all.

[yermulnik]

3. This works oddly on my end:

But seems any "--show-*" flag works in a same way when there is a .toml file provided

	case fileExists(TOMLConfigFile) || fileExists(HomeTOMLConfigFile):

in that case there is no --show flag check at all.

Oh, good catch. I missed this behavior =( Could you probably file an issue for this to get fixed (so that --show* flags don't actually switch TF version)? Thanks.

@warrensbox @jukie Any clue on whether this was implemented this way on purpose or this is indeed a bug?

[ikorchynskyi]

Created #302 to clarify the flags logic