Improve terminal profile selection

[msujew]

Feature Description:

Currently, except for the cmd terminal, no other terminal exists on Windows by default. Most users would expect to be able to find at least PowerShell in there. We should offer better default profiles there.

In addition to that, the current terminal.integrated.defaultProfile.{os} preferences current are simply text fields. In VS Code, these are drop downs:

We should align to that to improve the UX of the feature.