Enable connect-under-reset for st-util baremetal debugger

The st-util (since 1.6.1) supports restarting the target MCU before flashing. This option enables the connection to MCU even if the binary in it is sleep mode or JTAG pins are used otherwise.

I have evaluated this option by creating a wrapper script, that adds this option to the list of command-line arguments, and it would be great if the option was built-in into the bare metal plugin.