Add support for nvm for Windows

[JimiC]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	N/A
Fixed tickets	#3739
License	MIT

These are the minimum required changes to support nvm for Windows.

[CLAassistant]

All committers have signed the CLA.

[JimiC]

I'd like to explain lines 380-381 a bit as nvm for Windows has a quirk.
When it first downloads node.exe for a version, it renames it to node64.exe for x64 platforms and node32.exe for x32 ones, in order to support both arch side by side.
Upon activation via nvm use it renames nodeX.exe to node.exe and remains so if no other arch version for the same node version is downloaded.

Now, I wanted to refrain from making the codebase complex by introducing filename checks, so I kept it at a bare minimum which leads to a quirky flow.

Explaining.

pm2 will always look for a node.exe filename when trying to resolve the specified interpreter.

• If the user has already activated the node version, pm2 will see the node.exe file and proceed as normal.
• If the user has not downloaded the node version specified, pm2 will trigger an nvm install. As mentioned above nvm for Windows has that renaming quirk, so after the download is finished, pm2 will look for a node64.exe or node32.exe instead of node.exe, as the user has not yet activated that node version.
• If the user has previously downloaded the node version specified but has not activated it yet, the filename will still be nodeX.exe. pm2 will look for a node.exe filename but will not find it and will try to download that version again. Now, nvm for Windows will see that that node version is already there and prompt that the version already exists and skips download. This is when lines 380-381 come to the rescue as they tell pm2 to look for a nodeX.exe filename instead, which is true and pm2 then proceeds as normal.

If you think that this flow will cause maintainability issues, and you prefer a filename check function to be added instead, please let me know, so to update the PR.

[JimiC]

Unfortunately, no tests have been added, as you don't have a Windows testing environment, yet.