[Utils] Improved chunk-print-before-all.py script

As part of this patch, the ability to work with dump files
containing ir after passes received using the -print-after-all
option was added to script chunk-print-before-all.py.
The names of the output files have also been changed.
	Before: chunk-NUM.ll
	Now: NUM-STAGE-PASS_NAME.ll
NUM - sequence number of the pass operation.
STAGE - stage of the pass operation (for example: before, after, dump).
PASS_NAME - the name of the pass.