chore: use NSIS installer for windows [INS-3983]

[filfreire]

Related to INS-3983

In this PR we explore moving to NSIS.
Reasoning for moving to NSIS:

• Potentially fix Insomnia not having permissions to write on app data folder - NSIS allows to install insomnia on System-level instead of User's AppData level;
• According to electron-builder docs, squirrel is deprecated.
• Give user option of where to install Insomnia at.

Concerns:

• Auto-update behavior for existing users on past Squirrel builds
• Conflicting double-installations, e.g. an older one on %Appdata% existing at the same time as System level NSIS installs on C:/Program Files.

Related PR: #7838