Prior to this commit, the TestContextManager logged an exception from a
TestExecutionListener at WARN level except in prepareTestInstance()
where such an exception was logged at ERROR level (except for a skipped
exception which is logged at INFO level).
For consistency, this commit modifies TestContextManager so that it
always logs non-skipped exceptions from TestExecutionListeners at WARN
level.
Closes gh-31688
97264c77dd