Fix AudioPlayback testcase ID collision for LAVA CI

[tmoida]

Description

This PR fixes the testcase ID collision issue in LAVA by implementing flexible testcase naming for the AudioPlayback test suite, enabling parallel execution of multiple AudioPlayback configurations in CI.

Problem

LAVA was experiencing testcase ID collisions because:

• The AudioPlayback script was hardcoding the testcase name as AudioPlayback in the .res file
• When running multiple AudioPlayback configurations in parallel (e.g., Config01, Config03, Config05), all tests reported the same testcase ID
• LAVA expected unique testcase IDs like AudioPlayback_Config01, AudioPlayback_Config03, etc. based on the job definition
• This collision caused LAVA to overwrite test results and prevented proper CI enablement

Solution

Implemented a flexible testcase naming mechanism that allows LAVA to specify unique testcase IDs:

• Added RESULT_TESTNAME variable - Defaults to AudioPlayback but can be overridden via CLI parameter
• Added --lava-testcase-id parameter - Allows LAVA to specify unique testcase names for each configuration
• Added LAVA_TESTCASE_ID YAML parameter - Passes the testcase ID from LAVA job definition to the script
• Updated all result handling - Changed all .res file writes to use $RESULT_TESTNAME instead of $TESTNAME
• Pre-parse support - Early parsing of --lava-testcase-id ensures unique result files even if setup fails

[tmoida]

Here are the details of the validation job:
https://lava.infra.foundries.io/scheduler/job/174081