fix: properly handle directory, file, git and alias specs in overrides

[nlf]

the previous logic was a bit naive and assumed that the spec in use would always be a range or version. these changes allow directory, file, git and alias spec types to be overridden the same way as other types

related to #5007

[AlonNavon]

Any chance of backporting the fix to the latest version 8? @nlf
The overrides feature was introduced in 8.3.0, and it seems natural that the fix would be applied there as well.

[ljharb]

I believe 8 was EOL once 9 came out.

[AlonNavon]

Is there a place where this is documented? The npm documentation contains information all the way back to version 6.
More importantly, Node.js 16 still hasn't reached EOL (which is coming September 2023), and its npm version is 8.19.4.
So I think EOLing version npm 8 wasn't ideal, and considering the ease of the fix it would be helpful for a lot of people to do the backport. Version 8 is actually more popular than version 9 right now @ljharb

[ljharb]

My understanding is that anything that's not the latest major only gets security patches. It being included in a supported node line certainly means it would get those. I'll leave it to the npm folks to decide what they want to backport ofc, i just wanted to set expectations.