ci: fold output for test_build_caches

[SubaruArai]

Adds output folding for test/test_build_caches.py.

Related: #25334, #38167

[audrow]

This seems like a good idea to me. @clalancette, any thoughts?

[SubaruArai]

For future reference:

We might want to change how Fold enumerates the id for nested blocks.

# current
block 1 start
block 2 start
...
block 2 end
block 1 end

# proposed
block 1 start
block 1-1 start
...
block 1-1 end
block 1 end

[SubaruArai]

The CI failed with a url timeout error, can someone with the permission trigger a re-run?

=================================== FAILURES ===================================
____________________________ test_rosdep_duplicates ____________________________

url = 'https://raw.githubusercontent.com/ros/rosdistro/master/hydro/distribution.yaml'
retry = 2, retry_period = 1, timeout = 10, skip_decode = False

    def load_url(url, retry=2, retry_period=1, timeout=10, skip_decode=False):
        try:
>           fh = urlopen(url, timeout=timeout)

...

FAILED test/rosdep_duplicates_test.py::test_rosdep_duplicates - socket.timeout: The read operation timed out (https://raw.githubusercontent.com/ros/rosdistro/master/hydro/distribution.yaml)

[SubaruArai]

@clalancette ping