[SIGMON-557] addressing warning messages in pytest

Context

• With the new 'latest' testing environment, a lot of warning appeared
• Some of those warnings are also present in the SWAN testing environment
• To make the code future-proof (DeprecationWarning), and improve code quality (UserWarning), those warnings need to be addressed

What was done

• Capture warnings in tests that were generated by our code
• Use median_filter instead of medfilt to specify the mode parameter to 'constant' (default behaviour of medfilt but that raised a warning when used). This change should also improve performance (see medfilt)

TODO

• Some warnings remaining

QA

• no new code was written
• acceptance tests were written

Review objectives

• assessment of code functionality
• assessment of code quality
• 😄