1. Modify PinMode enum to fully support GPIO I/O modes.
2. Translate input pull mode/direction to I/O mode, where H/W doesn't support
separate configuration for input pull mode/direction.
3. Allow for configuring I/O mode in addition to input pull mode.
1. Rename m2351_stddriver_sup.h/c to stddriver_secure.h/.c for naming consistency
2. Add hal_secure.h to include hal-exported secure functions
3. Change return/argument type in secure functions:
(1) Change int to int32_t
(2) Change PinName to int32_t
(3) Change time_t to int64_t
4. Update secure lib/bin accordingly
1. Revise NU_PORT_BASE to be TrustZone-aware
2. Add TrustZone-aware NU_GET_GPIO_PIN_DATA/NU_SET_GPIO_PIN_DATA to replace GPIO_PIN_DATA
3. Revise pin_function to be TrustZone-aware