Update Pony musl Docker images to Alpine 3.20 #2798

Job	Run time
Lint bash, docker, markdown, and yaml	1m 43s
Validate GNU Docker image builds	33s
Validate musl Docker image builds	28s
Validate musl Docker release image builds	20s
Validate GNU Docker release image builds	30s
Validate Windows Docker image builds	2m 46s
Validate Windows Docker release image builds	2m 6s
Verify CHANGELOG is valid	7s
x86-64 Linux glibc	20m 50s
x86-64 Linux musl	23m 22s
aarch64 Linux glibc	22m 5s
arm64 Apple Darwin	15m 59s
armhf Linux glibc	27m 56s
arm Linux glibc	29m 28s
riscv64 Linux glibc	23m 12s
x86-64 Apple Darwin	32m 29s
x86-64 Windows MSVC	38m 16s
use dtrace	20m 42s
use pool_memalign	24m 22s
use runtimestats	21m 29s
	5h 8m 43s

Provide feedback