Change vsock's lingerning to wait on close() until all data is sent, i.e.
until workers picked all the packets for processing.

Changes in v2:
- Comment that some transports do not implement unsent_bytes [Stefano]
- Reduce the indentation of virtio_transport_wait_close() [Stefano] 
- Do not linger on shutdown(), expand the commit messages [Paolo]
- Link to v1: https://lore.kernel.org/r/20250407-vsock-linger-v1-0-1458038e3492@rbox.co

Changes in v1:
- Do not assume `unsent_bytes()` is implemented by all transports [Stefano]
- Link to v0: https://lore.kernel.org/netdev/df2d51fd-03e7-477f-8aea-938446f47864@rbox.co/

Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
Michal Luczaj (3):
      vsock: Linger on unsent data
      vsock: Reduce indentation in virtio_transport_wait_close()
      vsock/test: Expand linger test to ensure close() does not misbehave

 net/vmw_vsock/virtio_transport_common.c | 29 +++++++++++++++++++----------
 tools/testing/vsock/vsock_test.c        | 30 +++++++++++++++++++++++++++---
 2 files changed, 46 insertions(+), 13 deletions(-)
---
base-commit: 8066e388be48f1ad62b0449dc1d31a25489fa12a
change-id: 20250304-vsock-linger-9026e5f9986c

Best regards,
-- 
Michal Luczaj <mhal@rbox.co>