Fix test script paths (#3387)

* fix path to task executable in pyton tests

The current approach would copy the current files into the `build/test`
directory. Updating the paths according to the custom user setup.

By the copy I appended `.py` to have a clear visible distingtion which
ones are the python tests.

As soon as a source file in the normal directory is changed, it is
copied over and the corresponding file is updated.

From now on the python tests would need to get run in the according
build directory.

* reflect the current build instruction in PR template

* update paths and globing in run_all

* add line break for every cpp test

* remove .gitignore in test folder

As now all the auxillary files such as `all.log` as well as the
executables are present in the `build` directory there is no longer a
need to ignore them.

* update paths in python test scripts and enable deactivated

* remove .py extension when copy to build

Further remove glob pattern for `*.t.py` tests.

* remove accidentally added template.t from test files

.github/pull_request_template.md

@@ -5,7 +5,7 @@ Replace this text with a description of the PR.
 #### Additional information...
 
 - [ ] I changed C++ code or build infrastructure.
-  Please run the test suite and include the output of `cd test && ./problems`.
+  Please run the test suite and include the output of `cd build/test && make && ./problems`.
 
 - [ ] I changed Rust code or build infrastructure.
   Please run `cargo test` and address any failures before submitting.