fix: update Python target for Fable v5 compatibility

[dbrattli]

Changes required for using Thoth.Json with Fable v5-alpha, so we know what to do when Fable v5 stable is released.

• Update to Fable 5.0.0-alpha.21
• Use Fable.Python for Json handling since Fable v5 need special treatment of numerics
• Use uv for Python dependency and venv handling
• Use .NET 10

Tag: python

[MangelMaxime]

It seems like we have a bug in the compilation / runtime code:

But it seems like I am getting a runtime error:

.> uv run python fableBuild/main.py --silent
Traceback (most recent call last):
  File "/home/mmangel/Workspaces/Github/thoth-org/Thoth.Json/main/tests/Thoth.Json.Tests.Python/fableBuild/main.py", line 100, in <module>
    main(Array[Any](sys.argv[1:]))
    ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mmangel/Workspaces/Github/thoth-org/Thoth.Json/main/tests/Thoth.Json.Tests.Python/fableBuild/main.py", line 95, in main
    runner: PythonTestRunner = PythonTestRunner__ctor()
                               ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/mmangel/Workspaces/Github/thoth-org/Thoth.Json/main/tests/Thoth.Json.Tests.Python/fableBuild/main.py", line 91, in PythonTestRunner__ctor
    return PythonTestRunner(__unit)
TypeError: Can't instantiate abstract class PythonTestRunner without an implementation for abstract methods 'Thoth_Json_Tests_Testing_TestRunner_MapEncoderValueToDecoderValue2B594', 'Thoth_Json_Tests_Testing_TestRunner_get_Decode', 'Thoth_Json_Tests_Testing_TestRunner_get_DecoderHelpers', 'Thoth_Json_Tests_Testing_TestRunner_get_Encode', 'Thoth_Json_Tests_Testing_TestRunner_get_EncoderHelpers'
Compilation failed
Error: The command exited with code 1.

[MangelMaxime]

Finally ... I hate debugging CI