github: Use separate caches for custom-built dependencies

These are shared by many tests, in particular the "all", "coverage",
"no-dbg" and "no-testable-ke" tests, which each would otherwise require
their own large cache.

Similarly, the "codeql" and "sonarcloud" tests rely on the same
dependencies but only the latter uses ccache for the strongSwan build.

Also reduce the maximum size per cache for all workflows to keep them
in check over time (some could even be set lower, we'll have to see
how this develops).

.github/workflows/android.yml

@@ -12,7 +12,7 @@ permissions:
 env:
   CCACHE_BASEDIR: ${{ github.workspace }}
   CCACHE_COMPRESS: true
-  CCACHE_MAXSIZE: 400M
+  CCACHE_MAXSIZE: 150M
   CC: gcc
   OS_NAME: linux