These aren't used externally at all, so they can be made private.

Allows pushing strongly-typed enum members without the need to always
cast them at the call sites.

Note that we *only* allow strongly-typed enums in this case. The reason
for this is that strongly typed enums have a guaranteed defined size, so
the size of the data being pushed is always deterministic. With regular
enums this can be a little more error-prone, so we disallow them.

This function simply uses the underlying type of the enum to determine
the size of the data. For example, if an enum is defined as:

enum class SomeEnum : u16 {
  SomeEntry
};

if PushEnum(SomeEnum::SomeEntry); is called, then it will push a
u16-size amount of data.

- This can be used for domain objects as inputs to service functions.

* Stub PopLaunchParameter and implement Buffer C Descriptors reading

* Address PR feedback

* Ensure we push a u64 not a size_t

* Fix formatting

They should have 32 bits of padding after the error code now.

Popping objects from the buffer is still not implemented.

IPC: Use the correct size when pushing raw data to the command buffer and fixed pushing domain objects.

Domain object ids are always stored immediately after the raw data.

Reduces the necessary allocation to max(in_handles, out_handles) rather
than (in_handles + out_handles).

These use the context functions to create and look-up handles for the
user.