[dev-alloc] Support mixed data types

[deyuan]

Examples of mixed data type operations:

• Type conversion
• int32 * int32 -> int64
• int32 cmp int32 -> bool
• ...

PIM simulation considerations:

• Support both V and H layouts
• Support various PIM architectures

PIMeval code designs:

• Allocation
  • Allow a narrower data type to be associated with a wider data type, but not vise versa which is not possible for H layout
  • Each element has an actual bit width and a padded bit width. PIM commands need to locate elements using padded bit width and access data using the actual bit width
  • PIM data copy need to consider sign extension or pad with zeros
• Bool type
  • Decide to store 1 or 8 bool in each byte
  • std::vector<bool> has no .data() method

Related to Issue #16, #20, #74