Stability batch (see description)

[soronpo]

• Prepare for Scala 3.4.2 and 3.5.0-RC1 releases.
• Better error handling to enable exception instead of exit with options.onError
• Proper Vector/Struct/Opaque type conversions.
• Only include local conversion functions when needed (global types always have them).
• Vector index and shift types are now DFHDL integers.
• Fixes Error in VHDL code gen when vectors are part of struct #141
• Fixes VHDL array indexing requires to_integer function #142

There are still other issues to solve;

• VHDL enum conversions
• Verilog Vector/Struct composition and conversion.