MINOR: tools: add new function dump_addr_and_bytes()

MINOR: tools: add new function dump_addr_and_bytes()

This function dumps <n> bytes from <addr> in hex form into buffer <buf>
enclosed in brackets after the address itself, formatted on 14 chars
including the "0x" prefix. This is meant to be used as a prefix for code
areas. For example: "0x7f10b6557690 [48 c7 c0 0f 00 00 00 0f]: "
It relies on may_access() to know if the bytes are dumpable, otherwise "--"
is emitted. An optional prefix is supported.