Cleanup the hyperlight-host public API

Currently the following items are publicly exported from hyperlight-host, and I believe many of them were never intended to be public, we should fix that.
For items that are not intended to be public, but are needed by macros, we should mark them as `#[doc(hidden)]`, and ideally be moved to a properly named module, something like `_private`

Crossed out are the items I believe don't need to be public.

# List of all items
## Structs
- [ ] func::HostFunction
- [x] ~~hypervisor::VirtualCPU~~
- [x] ~~mem::memory_region::MemoryRegion~~
- [x] ~~mem::memory_region::MemoryRegionFlags~~
- [x] ~~mem::ptr::RawPtr~~
- [x] ~~mem::shared_mem::ExclusiveSharedMemory~~
- [x] ~~mem::shared_mem::GuestSharedMemory~~
- [x] ~~mem::shared_mem::HostMapping~~
- [x] ~~mem::shared_mem::HostSharedMemory~~
- [ ] sandbox::config::SandboxConfiguration
- [ ] sandbox::initialized_multi_use::MultiUseSandbox
- [ ] sandbox::snapshot::Snapshot
- [ ] sandbox::uninitialized::GuestBlob
- [ ] sandbox::uninitialized::GuestEnvironment
- [ ] sandbox::uninitialized::UninitializedSandbox
## Enums
- [ ] error::HyperlightError
- [ ] func::ParameterValue
- [ ] func::ReturnType
- [ ] func::ReturnValue
- [x] ~~hypervisor::HyperlightExit~~
- [x] ~~mem::memory_region::MemoryRegionType~~
- [ ] sandbox::uninitialized::GuestBinary
## Traits
- [ ] func::ParameterTuple
- [ ] func::Registerable
- [ ] func::ResultType
- [ ] func::SupportedParameterType
- [ ] func::SupportedReturnType
- [ ] hypervisor::InterruptHandle
- [x] ~~mem::shared_mem::AllValid~~
- [x] ~~mem::shared_mem::SharedMemory~~
- [ ] sandbox::Callable
## Macros
- [x] ~~and~~
- [x] ~~debug~~
- [ ] log_then_return
- [ ] new_error
- [X] ~~or~~
## Functions
- [x] ~~sandbox::is_hypervisor_present~~
- [x] ~~sandbox::is_supported_platform~~
## Type Aliases
- [ ] Result
- [ ] sandbox::ExtraAllowedSyscall