hal::stm32f1 pin configuration should throw if the pin is already configured

[kammce]

This would allow applications to detect if there are pin conflicts in the system. By doing this at the pin configuration level, no other APIs in the code need to do any sort of checking themselves.

[kammce]

Already configured means not the default. The default should be "general purpose input with pull up" but this will need to be determined.

The behavior should be that pin configure checks if the pin is set to default, if it is, then configure it to the desired values. If it is not set to default, then throw an exception.

Configuring a pin multiple times as general purpose input with pull up is acceptable and will be allowed.