This commit fixes a bug in no-split and allow-split ring buffers free buffer size calculation.
When the free size available in the buffers less than the size of one item header,
the function prvGetCurMaxSizeNoSplit/AllowSplit() incorrectly returned the maxItemSize instead of 0.
This is due to the comparision between a negative and a positive value
where both operands are treated as unsigned during the comparision operation,
thereby treating the negative operand as a large integer.
Also added new unit tests to test buffer-full and almost-full conditions
where this scenario is likely to be hit.
Closes https://github.com/espressif/esp-idf/issues/7344
Closes https://github.com/espressif/esp-idf/pull/7371
New unity component can be used for testing other applications.
Upstream version of Unity is included as a submodule.
Utilities specific to ESP-IDF unit tests (partitions, leak checking
setup/teardown functions, etc) are kept only in unit-test-app.
Kconfig options are added to allow disabling certain Unity features.
In earlier change this component was decoupled from freertos and hence
regression was introduced which changed default placement to flash. Some
device drivers make use of ringbuffer while flash cache is being disabled
and hence default placement should instead be internal memory.
Closes: https://github.com/espressif/esp-idf/issues/2517
