Use uv `centralized-project-envs` preview instead of `UV_PROJECT_ENVIRONMENT`

[coretl]

When astral-sh/uv#18214 is released, then we will be able to get uv to store its venvs in its cache directory. This means we should be able to remove the following settings:

python-copier-template/.devcontainer/devcontainer.json

Lines 16 to 29 in 7fa903a

	"UV_PROJECT_ENVIRONMENT": "/cache/venv-for${localWorkspaceFolder}",
	// Do the equivalent of "activate" the venv so we don't have to "uv run" everything
	"VIRTUAL_ENV": "/cache/venv-for${localWorkspaceFolder}",
	"PATH": "/cache/venv-for${localWorkspaceFolder}/bin:${containerEnv:PATH}"
	},
	"customizations": {
	"vscode": {
	// Set *default* container specific settings.json values on container create.
	"settings": {
	// Use the container's python by default
	"python.defaultInterpreterPath": "/cache/venv-for${localWorkspaceFolder}/bin/python",
	// Don't activate the venv as it is already in the PATH
	"python.terminal.activateEnvInCurrentTerminal": false,
	"python.terminal.activateEnvironment": false,

This ticket is to try this out when a new uv is released and available in ubuntu-devcontainer