build: refactor version info and icon resource handling on windows

This makes it easier to add resources with any build method, and also when
building librclone.dll.

Goversioninfo is now used as a library, instead of running it as a tool.

.github/workflows/build.yml

@@ -216,7 +216,6 @@ jobs:
         shell: bash
         run: |
           if [[ "${{ matrix.os }}" == "ubuntu-latest" ]]; then make release_dep_linux ; fi
-          if [[ "${{ matrix.os }}" == "windows-latest" ]]; then make release_dep_windows ; fi
           make ci_beta
         env:
           RCLONE_CONFIG_PASS: ${{ secrets.RCLONE_CONFIG_PASS }}