percona: adapt upstream release model

In accordance to the upstream release cycle, we now provide 2 flavours
of the percona mysql ecosystem. The default is the LTS variant,
additionally there is now the floating `percona-server_innovation`
always pointing to the most recent regular release.

- mentioned in release notes
- adapted all depending tests and tools (xtrabackup)

nixos/tests/mysql/mysql.nix

@@ -146,7 +146,6 @@ in
   }) mariadbPackages)
   // (lib.mapAttrs (_: package: makeMySQLTest {
     inherit package;
-    # FIXME: packages are renamed soon anyways
-    #name = package.pname;
+    name = builtins.replaceStrings ["-"] ["_"] package.pname;
     hasMroonga = false; useSocketAuth = false;
   }) perconaPackages)