[feat] - remove unused electron installations

[TsMonkeyPatch]

Is your feature request related to a problem? Please describe.
This could install (download) multiple electron installation which takes to much space on hard disk.

Describe the solution you'd like
Ensure an electron which is not used would be deleted (excluding global installations) should be deleted after they are not used for @example 2 weeks.

[muzam1l]

There is definitely need for better version management in this extension for it to be practically useful. Instead of checking usage last time, it should keep track of which "dependent extension" triggered download, and when that extension is disabled or uninstalled, its electron version should be removed. Likewise to keep size in check, one extension should only have one electron version and if it downloads newer version, old one should be removed.

And most important of all, nobody needs exact electron version up to minor patch, there has to be sematic version control. Extension devs would simply specify something like ^12.0.1 and if any version available specifies that need, no need to download.

While all of this is implemented, just expose installedVersions array for now, so extension devs can can take decision to download or not themselves.