Add optimization level in i2copt3001_cpp GCC example to avoid stack overflows on interrupt.

CC13X2 and CC26X2 devices, the i2copt3001_cpp GCC example overflows the stack of the idle task and alarm task when an interrupt is received. The stacks were sized with optimisation turned on. Turning it off causes increased stack usage.
All GCC, TI Clang, and TI ARM examples across all devices now have optimisation enabled by default:

• GCC: -O3
• TI Clang: -Oz
• TI ARM: - O3