The `readMemory` request used the `MemoryRegionInfo` so it could also
support short reads. Since #106532, this is no longer necessary, as
mentioned by @labath in a comment on #104317.
With this commit, we no longer set the `unreadableBytes` in the result.
But this is optional, anyway, according to the spec, and afaik the
VS Code UI does not make good use of `unreadableBytes`, anyway.
We prefer `SBTarget::ReadMemory` over `SBProcess::ReadMemory`, because
the `memory read` command also reads memory through the target instead
of the process, and because users would expect the UI view and the
results from memory read to be in-sync.
786dc5a2da