When specifying a script file in the BSF post-processor, the filename is treated as a code snippet instead of being loaded, taking precedence over the regular script.

This likely also affects the BSF Preprocessor, Assertion, and Listener, as they all call the BSFTestElement.processFileOrScript(BSFManager) method. The processFileOrScript method currently takes the filename and passes it directly to the script manager for evaluation instead of loading the file and passing its contents to the script manager.

Steps to Reproduce:
 - Create new Test Plan
 - Add a new Thread Group
 - Add a new sampler (tested with a Debug Sampler)
 - Add a new BSF Postprocessor
 - Choose an available BSF language (Tested with "javascript")
 - Input valid javascript as filename (Tested with OUT.println("--- filename ---"))
 - Input valid javascript as script (Tested with OUT.println("--- script ---");)
 - Execute test

Expected Results:
 - Postprocessor fails, unable to find file

Actual Results:
 - Console output: "--- filename ---"