Revert search based on qpart and QRegExp.
qpart can't find \n between blocks.

This reverts commit 97caf9d128eca41b0f58262bf1254a9e2e73cd43.
This reverts commit b579ea3af71a345179338910053ce34cb561bb10.
This reverts commit 3ebe364d65263a5b00cce26c424d29d9c0454402.
Search in file performance optimization