Support port default value

[taichi-ishitani]

This PR is to add port default value support.
We can specify a default value which is used when the connection to this port is omitted.
Currenlty, following factors can be used for a port defualt value.

• For input port
  • literal
  • const defined in a package
• For output port (module)
  • anonymous identifier
  • this port is opened if connection is omitted
• For output port (function)
  • Not allowed
• For other ports
  • Not allowed

close #1086

[codspeed-hq]

CodSpeed Performance Report

Merging #1164 will not alter performance

_{Comparing taichi-ishitani:default_port_value (d0e303f) with master (1bff7d0)}

Summary

✅ 3 untouched benchmarks