Refactor smoke_test.py test fixtures

[jcar87]

Description

Refactor fixtures such that each test uses its own cmake source and build directory, rather than reusing them across tests. This helps those tests that need to mutate the source directory, and also prevents pytest-ordering issues or workarounds by never reusing a build directory.

Motivation

The session scope basic_setup and the tmpdirs fixture, on top of setting up a CONAN_HOME that is custom to the entire test session, set the current working directory of all tests to be the same. The function-scope fixtures chdir_build and chdir_build_multi then simply chdir into either build directory. Additionally, the conan provider is copied to this working directory alongside the sources. This has some problems:

• The structure of the basic cmake project for testing is common to all tests. This would be fine, however, some tests mutate the contents of this "source" directory - so tests run after would be configuring an entirely different project. If it has worked so far, it's by coincidence.
• The build directory is reused between tests - this has resulted in tests that need a clean state to either pass --fresh to the cmake invocation (to ignore anything that was there beforehand), or to have class-scope fixtures to delete the contents of the build directory, if it exists. One test, however, relies on an already initialized build directory to exist.

Detailed changes

• Separate concerns by creating two new fixtures that are global to the session:
  • conan_home_dir: sets the CONAN_HOME environment variable
  • setup_conan_home: exports the relevant recipes
• Use pytest's built-in tmp_path_factory or tmp_path fixtures, rather than doing this manually via tempfile - pytest handles the automatic deletion of past temporary directories and there's no need to do that ourselves.
• Create a basic_cmake_project test-level fixture:
  • Create a per-test temporary working directory
  • Call setup_cmake_workdir() (new function) to copy the contents of the basic cmake project for testing
  • Create a build folder, and chdir into it
  • This is unique to each test that uses this fixture, so neither the source folder nor the build folder are reused.
• For tests that need a different setup, they can opt to not use the test-level fixture, and handle this differently.
• Use a global variable for the path to the conan_provider.cmake file - It's static and is not mutated by any of the tests, and it doesn't need to be copied.

Refactors:

The above changes enable the following:

• The TestBasic class assumes a re-used build directory, and a separate build-multi directory - this is now handled in a new setup_basic_test_workdir() class-level fixture. This is done to enable minimal changes to the already existing tests in this class
• Refactor all find module tests into a single class - there's no no longer a need to be in different classes each with a different class-scope fixture - since each test uses basic_cmake_project, each can mutate the contents of the source directory by copying the extra files from the resources directory.
• The TestSubdir uses a custom setup (different resources) - so handle it with a custom fixture in that class
• Refactor TestSubdir to support Windows - there's no reason why it wasn't supported
• Remove all workarounds passing --fresh to CMake - they're all fresh now, because the build directory is empty when using the basic_cmake_project fixture
• Remove workarounds clearing the contents of the build directory in a fixture - no longer needed, since it's guaranteed to be empty when using basic_cmake_project.

[memsharded]

Looking solid

[juansblanco]

Looks good.
We could group all the 'module' resources in a parent folder since the tests that use them are all in the same class now.