Report conformance outcomes from Yields() through link-time seams.

Yields() used to ask the ledger to judge and tally a result in one call,
and the fixture's TearDown() hooks turned the tallies into test
properties.  Now Yields() asks the global FailureList for the verdict (a
read, see GetGlobalFailureList()) and reports the outcome through
ReportSuccess(), ReportFailure() or ReportSkip(); that is the one write
the matchers make, and the two are kept apart on purpose.  The ledger
counts each conformance test once, so the matcher no longer keeps track
of earlier checks: gtest's second evaluation of a failing matcher, to
explain the failure, changes nothing.  A ResultListener the environment
registers with gtest records each test's and suite's statistics as their
properties when they end, so the fixture loses its TearDown() hooks and
nothing but the environment and Yields() touches the ledger.

A process-wide ledger is safe because gtest runs the tests of a binary
one after the other; a sharded run is several processes, each with its
own environment and ledger (global_test_environment.h spells this out).

Visible consequence: a result checked a second time is judged on its own
but never counted, instead of failing the test.  The integration test
now also checks, end to end, that a listed test that passes fails the
run, that --enforcement_level tolerates exactly the P1 failures and that
a sharded run skips the unseen-entries check.

PiperOrigin-RevId: 994487363