Improve dtype type hints with type stubs

[tbennun]

This PR stops the mypy/pyright warnings when using dace.* types, and also shows them as numpy arrays for code completion purposes.

[pratyai]

(I ran pyright over the project out of curiosity. No action needed, just FYI)
pyright report: https://polybox.ethz.ch/index.php/s/5oSFR3tQTR9FD2y
from this config:

~/g/main-dace (typehint-nowarn|✔) $ cat pyrightconfig.json 
{
  "include": [
    "dace",
    "tests",
    "samples",
    "tutorials",
    "setup.py"
  ],
  "exclude": [
    "**/__pycache__",
    ".dacecache",
    "build",
    "dist",
    ".git",
    "**/.*"
  ],
  "venvPath": ".",
  "venv": ".venv",
  "pythonVersion": "3.14",
  "typeCheckingMode": "strict",
  "reportMissingTypeStubs": true,
  "reportUnusedImport": false
}

[tbennun]

@pratyai looks like mostly localized missing type hints. I'd leave that for another PR