Introduced jemalloc (#5590)

### What problem does this PR solve?

Introduced jemalloc.
Python uses pymalloc (which is an reimplementation of gblibc malloc) to
manage RES. It has pools for small objects to avoid returning memory to
OS aggressively. My experience is: Replacing pymalloc with
[jemalloc](https://github.com/jemalloc/jemalloc) can reduce RES and
speedup task_executor.py.

### Type of change

- [x] Performance Improvement

Dockerfile

@@ -59,6 +59,7 @@ RUN --mount=type=cache,id=ragflow_apt,target=/var/cache/apt,sharing=locked \
     apt install -y default-jdk && \
     apt install -y libatk-bridge2.0-0 && \
     apt install -y libpython3-dev libgtk-4-1 libnss3 xdg-utils libgbm-dev && \
+    apt install -y libjemalloc-dev && \
     apt install -y python3-pip pipx nginx unzip curl wget git vim less
 
 RUN if [ "$NEED_MIRROR" == "1" ]; then \