tools: Add test-main equivalent for Powershell on Windows.
ADD
tools/test-main.ps1
+Set-StrictMode -Version Latest
+$ErrorActionPreference = "Stop"
+
+python tools\test-bots "$args" --coverage
+python tools\test-botserver "$args" --coverage combine
+python tools\test-zulip "$args" --coverage combine
+python tools\test-lib "$args" --coverage combine

tools: Add test-main equivalent for Powershell on Windows.