Options for persistence of memory in `MemoryModel`

[mkorbel1]

Motivation

Currently, invalid accesses or resets to a MemoryModel cause clearing of memory contents. There are scenarios where this might be annoying (e.g. modelling a ROM or a memory that has it's own reset characteristics).

Desired solution

More configurability and options around reset, invalid accesses, etc. for memory models.

Alternatives considered

No response

Additional details

No response

[mkorbel1]

Thanks to @RossComputerGuy who motivated this ticket on Discord (https://discord.com/channels/1001179329411166267/1001179329411166270/1451299527842861087).