Update CMSIS-pack info for STM32G-family

Update the CMSIS-pack info to `index.json` in arm_pack_manager -folder.
The update happens via python project.py --update-packs and a modified
version of the cmsis-pack-manager tool, which allows the download of
(most) CMSIS-pack files. The changes for this family ONLY are then updated
to the `index.json` -file.

Mbed OS PR #12093 need this change, as they refer to a target (device_name)
from the updated CMSIS-packs.

Ref: #12093

Author: Janne Kiiskila