fix: make map types public

[simongdavies]

This pull request fixes visibility in the memory region handling code in src/hyperlight_host/src/mem/memory_region.rs for hyperlight-wasm use.

Visibility improvements:

• Made the MemoryRegionType enum public, allowing it to be used outside of the current crate.
• Made the SurrogateMapping enum public, so it can be accessed from other modules or crates.
• Made the surrogate_mapping method on MemoryRegionType public, enabling external code to determine the surrogate mapping for a given memory region type.

[jsturtevant]

Need to make the field on MemoryRegion pub as well:

      let rgn = MemoryRegion {
    |                   ------------ in this type
...
127 |             region_type: MemoryRegionType::Heap,
    |             ^^^^^^^^^^^ private field

Maybe a integration test that uses map_region would be a good addtion? I should have done this when we ran into it before #1293

[jsturtevant]

verified the latest changes work in HL-wasm