Various Python refactorings as prerequirements for PY-65425 and PY-78035.

1. Make SDK->Module association function `suspend` to make it testable (one can't test something that runs code by `invokeLater`)
2. Add SDK->Module associations checks into `ensureSdkIsUsable` test tool.
3. Rename fields in v2 widgets to emphasize their purpose.
4. Make this association default for `pyVenv` fixture.

GitOrigin-RevId: 58267750b6dda0b596183c8bd335ce75b00fd41d

python/python-venv/tests/com/intellij/python/community/impl/venv/tests/pyVenvFixture.kt

@@ -15,6 +15,7 @@ import com.intellij.testFramework.junit5.fixture.testFixture
 import com.jetbrains.python.PythonBinary
 import com.jetbrains.python.getOrThrow
 import com.jetbrains.python.sdk.persist
+import com.jetbrains.python.sdk.setAssociationToModuleAsync
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import java.nio.file.Path
@@ -38,6 +39,7 @@ fun TestFixture<SdkFixture<PythonBinary>>.pyVenvFixture(
       venvSdk.persist()
       if (module != null) {
         ModuleRootModificationUtil.setModuleSdk(module, venvSdk)
+        venvSdk.setAssociationToModuleAsync(module)
       }
     }
     initialized(venvSdk) {