This patch replaces the direct interaction with the packet stream of
the block session by the use of the 'Block::Connection::Job' API,
removing the reliance on blocking packet-stream semantics.
Since I/O signals can now occur during 'Backend::submit', the patch
conditions the periodic calls of 'rump_sys_sync' by taking the backend
state into account.
Issue #4390
This patch changes the 'Allocator' interface to the use of 'Attempt'
return values instead of using exceptions for propagating errors.
To largely uphold compatibility with components using the original
exception-based interface - in particluar use cases where an 'Allocator'
is passed to the 'new' operator - the traditional 'alloc' is still
supported. But it existes merely as a wrapper around the new
'try_alloc'.
Issue #4324
This patch changes the 'alloc_aligned' interface as follows:
- The former 'from' and 'to' arguments are replaced by a single
'range' argument.
- The distinction of the use cases of regular allocations vs.
address-constrained allocations is now overed by a dedicated
overload instead of relying on a default argument.
- The 'align' argument has been changed from 'int' to 'unsigned'
to be better compatible with 'addr_t' and 'size_t'.
Fixes#4067
