Change VCP_* pin names to T_VCP_*.

Change VCP_* pin names to T_VCP_*.

According to the User Manual of the STLINK-V3SET pins 13 and 14 (Virtual COM Port pins) are called T_VCP_RX and T_VCP_TX. The 'T_' prefix stands for 'Target'. This is unconventional, as usually UART pins are named from the debugger's perspective. However, the 'T_' prefixes are omitted from the pin names in the library symbol. The pin directions are set correctly, however GPIO pins of MCUs used for the UART peripheral are commonly set as bidirectional, ERC won't catch it if they're flipped.

This merge request should reduce the probability of these pins being incorrectly connected, by explicitly stating these are named with respect to the target, not the debugger. Also updated the datasheet link.