Add standard stream to CMSIS-Driver USART retarget implementation

[VladimirUmek]

No description provided.

[VladimirUmek]

This PR consists of two commits:

• the first commit only changes the structure of the source directory.
• the second commit adds components for retargeting to the CMSIS Driver USART.

New components:

• STDERR:UART&CMSIS
• STDIN:UART&CMSIS
• STDOUT:UART&CMSIS

So each stream gets component "UART" and implementation variant "CMSIS" (using CMSIS-Driver USART API).

Files:

• stdio_cmsis_uart.c is the implementation file (STDIO -> UART) and is part of the CORE component. It is included in the project only if one of the STDERR/IN/OUT:UART components is selected.
• stdio_cmsis_uart_config.h configured which CMSIS-Driver USART driver instance is selected for STDIO. It automatically selects preconfigured instance from board layer
• std{err/in/out}_cmsis_uart_config.h are per-stream configuration files and are brought to the project when STD*:UART&CMSIS component is selected.

Defaults:

• STDIN buffers 64 bytes of incoming UART bytes
• STDERR/STDOUT are unbuffered

Configuration files offer option to generate CR after each LF for STDERR/STDOUT and offer option to echo STDIN to STDOUT.

[RobertRostohar]

LGTM