[FEATURE] Add option to use initial values for storage elements

[amykyta3]

Many FPGA architectures allow RTL to contain initial values for storage elements.
Use of these can significantly simplify designs since they provide the opportunity to eliminate hardware-based reset controls.

Provide the option to use initial values for the field storage elements. One idea would be to make this a command-line option --use-init (and also mirror this as a TOML config setting)

Other considerations:

• Init value would use the field's reset value
• If no reset value specified, assign "X" (required since this would be a struct initialization)
• May want to do the same for cpuif and other glue logic storage elements.
• May be interesting to provide the option to override the default reset signal to eliminate it entirely
• Users should still be able to provide specific hardware resets using field_reset/resetsignal and cpuif_reset mechanisms.