As $(OutputPath) is not absolute path, we need to add $(MSBuildProjectDirectory)

Tested:

• Create a new WebAssembly Browser App on VS and run, change WasmAppDir and run again.
• Create a new WebAssembly Console App on VS and run, change WasmAppDir and run again.
• Create a new wasmbrowser app using command line and run;
• Create a new wasmconsole app using command line and run;
• Create a new wasmbrowser app using command line and dotnet build and dotnet run --no-build;
• Create a new wasmbrowser app using command line and dotnet build and dotnet run --debug;

Also, added tests for command line runs. But a few of the tests are disabled because the tests would be using 7.0 targets, but 7.0 doesn't have the fix yet.

Fix #75356