feat: support plain old node as strategy to get node version

[matthewadams]

Support node --version as a strategy to get the node version. Current code assumes nvm is in use.

Description

Add function node_native_version_prompt to use node --version & refactor node_version_prompt to use new envvar NODE_VERSION_STRATEGY with values nvm (default) or node to call either nvm_version_prompt or node_native_version_prompt, respectively.

Motivation and Context

Current code assumes nvm manages node. I use asdf.

How Has This Been Tested?

Tested locally.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.

[matthewadams]

FYI, existing tests pass, but there are no tests for powerline's node prompt text. Just trying to get a quick & dirty done here. Default behavior is backward compatible.

[cornfeedhobo]

When ever we touch stuff related to language interpreters, I like to bring up the need to support shims, which is how a lot of these version managers work now.

[matthewadams]

When ever we touch stuff related to language interpreters, I like to bring up the need to support shims, which is how a lot of these version managers work now.

What does this mean with respect to this PR?

[NoahGorny]

Hi @matthewadams, thanks for your contribution!
I left a comment, but I am looking forward to merge this :)

[seefood]

seems simple enough...