Ring buffer completion passes incorrect length

[Alan-Jowett]

Resolves: #2656

Description

1. Ringbuffer async completion passes the wrong length for the output buffer.
2. IO Manager mock doesn't correctly copy the buffers to and from kernel mode in the async path.
3. Add instrumentation to test to catch duplicate records being returned.

Testing

Fixed existing tests to correctly catch this.

Documentation

No.

[codecov]

Codecov Report

Merging #2704 (e9d5602) into main (78f826c) will increase coverage by 0.00%.
The diff coverage is 97.82%.

@@           Coverage Diff           @@
##             main    #2704   +/-   ##
=======================================
  Coverage   83.13%   83.13%           
=======================================
  Files         146      146           
  Lines       28070    28103   +33     
=======================================
+ Hits        23336    23364   +28     
- Misses       4734     4739    +5     

Files Changed	Coverage Δ
tests/libs/common/common_tests.h	100.00% <ø> (ø)
tests/libs/common/common_tests.cpp	93.10% <90.90%> (-1.24%)	⬇️
libs/execution_context/ebpf_maps.c	90.44% <100.00%> (+<0.01%)	⬆️
tests/api_test/api_test.cpp	98.31% <100.00%> (+<0.01%)	⬆️
tests/end_to_end/test_helper.cpp	87.00% <100.00%> (+0.66%)	⬆️
tests/socket/socket_tests.cpp	98.88% <100.00%> (ø)

... and 2 files with indirect coverage changes