Update scripts
Major scripts refactoring

* Add support for both Erlang 15 and Erlang 17.
* Heavily refactor `prepare-tools-*.bash` to use `_do_exec` instead of manual environment variable management.
* Fix `prepare-tools-{ninja,maven}-cache.bash` to not fail on missing package folders. (Fixes a cyclic dependency in `tasks-all`.)
* Update `tasts-all.bash` in accordance with new RPM package names.
* Add support for either `!bash` or `!exec` in tasks.
* Include `pallur_distribution_version` in temporary folder path.
* Add support for `.local-env.bash`.
* Add support for some `pallur_*` variables to be set to `*` (which disables `.local-*` behaviour).
* Rename `.exec` and `.bash` to `_do-bash` and `_do-exec`.
* Rename `_script_*` functions to `_do_*`.