Add unit tests for allocation errors

[gavv]

Many pipeline elements take core::IArena as an argument and perform some allocations in constructor. If allocations fails, the convention is to report error (StatusNoMem) via init_status() method.

We need to cover this behavior with unit tests. For each element, we need to add one test that creates the element using mock, which always fails (e.g. core::NoopArena). Then we should check that the element returned StatusNoMem via init_status().

Elements to cover:

• ChannelMapperReader
• ChannelMapperWriter
• PcmMapperReader
• PcmMapperWriter
• ProfilingReader
• ProfilingWriter
• Mixer