Add PEP 723 support for SuiteSparse and SUNDIALS installation script

Introduce a TOML-style comment block at the top of the `install_KLU_Sundials.py` script. This block contains essential metadata, including the required Python version and a list of dependencies. This addition aligns the script with the PEP 723 guidelines, enhancing readability and portability for script runners and developers.

The metadata includes:
- The Python version requirement (<=3.9)
- Dependencies required for the script (wget, cmake)
- Additional information like the repository and documentation links

This enhancement facilitates easier script sharing and collaboration, providing a standardized way to specify and access script dependencies and supported Python versions. It also lays the groundwork for potential future tooling that could automate environment setup and dependency installation.

Refer to PEP 723 for more details on this format.

Resolves: pybamm-team#3647

scripts/install_KLU_Sundials.py

@@ -1,3 +1,15 @@
+# /// pyproject
+# [run]
+# requires-python = "<=3.9"
+# dependencies = [
+#   "wget",
+#   "cmake",
+# ]
+#
+# [additional-info]
+# repository = "https://github.com/pybamm-team/PyBaMM"
+# documentation = "https://docs.pybamm.org"
+# ///
 import os
 import subprocess
 import tarfile