Replace release.mk by release scripts

Since commit 2687d20280, the Makefile
named release.mk stopped handling dependencies between recipes, because
they have to be executed separately (from different Github Actions
jobs).

Using a Makefile no longer provides any real benefit. Replace it by
several individual release scripts for simplicity and readability.

Refs #5306 <https://github.com/Genymobile/scrcpy/pull/5306>
PR #5515 <https://github.com/Genymobile/scrcpy/pull/5515>

release/test_server.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+set -ex
+cd "$(dirname ${BASH_SOURCE[0]})"
+. build_common
+cd .. # root project dir
+
+GRADLE="${GRADLE:-./gradlew}"
+
+"$GRADLE" -p server check