[Task Processor] Prepare for "chain task" merge - Add a finally callback

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Service] Prepare for "chain task" merge - Provide access to global task processor

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Tasks] Reuse task processor engine for device construction internal tasks (old chain-task)

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Tasks] Reuse task processor engine for playlist internal tasks (old chain-task)

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Tasks] Remove obsolete chain-task.[ch] files

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Coding conventions] a few fixes

Signed-off-by: Regis Merlino <regis.merlino@intel.com>