pshell v2.1.4 (pico+pico2)

What's new in version 2.1.4

• Revert to merged cc_externs and cc_defs
• Update FUNCTIONs documentation
• Add hardware UART function and defines
• Expand heap size to maximum
• RP2350 peep hole addition + misc text diffs
• Improve peep hole optimizer logic