Removed CurlHandlerPool and simplified it #2182

Job	Run time
macos12	18m 56s
clang-tidy	3m 54s
MemoryTest (glibc_debug)	12m 4s
Linux (ubuntu:24.04)	11m 25s
MemoryTest (sanitize_address)	13m 29s
Linux (ubuntu:22.04)	11m 53s
MemoryTest (sanitize_others)	11m 57s
Linux (ubuntu:20.04)	11m 10s
MemoryTest (sanitize_thread)	12m 57s
Linux (debian:bookworm)	11m 47s
MemoryTest (thread_safety)	12m 0s
Linux (debian:bullseye)	11m 18s
MemoryTest (valgrind)	24m 23s
Linux (rockylinux:9)	12m 18s
Linux (rockylinux:8)	12m 35s
Linux (fedora:40)	11m 24s
Linux (fedora:39)	12m 39s
Linux (opensuse/leap:15)	12m 30s
Linux (alpine:3.20)	11m 38s
Linux (centos:centos7)	39m 5s
	4h 39m 22s

Provide feedback