chore: enable context reporting in coverage

coverage.py version 5.0 introduced the notion of measurement contexts.
This adds details to the report to show:

- how many times a given line was executed
- which context executed a given line

Enabling dynamic context measurement during the test execution adds
test class/function contexts to the coverage data to be displayed on
a given report output.

Refs: https://coverage.readthedocs.io/en/6.3.2/contexts.html#dynamic-contexts

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

.coveragerc

@@ -1,5 +1,6 @@
 [run]
 branch = True
+dynamic_context = test_function
 
 source =
     warehouse

bin/tests

@@ -34,5 +34,5 @@ set -x
 
 # Actually run our tests.
 python -m coverage run -m pytest --strict-markers $COMMAND_ARGS
-python -m coverage html
+python -m coverage html --show-contexts
 python -m coverage report -m --fail-under 100