* Run make ensure on devcontainer creation
Added an ensure target to the dotnet makefile to run `dotnet restore`.
* Add dotnet test explorer and set default vscode settings for it
* Ensure PULUMI_LOCAL_NUGET exists
* Add missing mkdirs
Currently this is just setting go.buildTags to "all" so the language
specific tests are included in build and test commands by default.
Missing this leads to the confusing (at least to new people) behavior
of clicking run test on a test method and vscode then saying there is no
test to run.
