test: Update to latest stable Alpine release (3.19)

Alpine 3.11 has been EOL since 2021-11-01 and there's no
incompatibilities with the 3.19 version. The only fix needed is to use
the latest stable Gerrit 3.5 release in order to pick up some SSHD
fixes.

Change-Id: I4212a714af2c5ac5556d479139bf2097d9f0952b
2 files changed