Make error handlers treat any failures as fatal

A lot of existing tests that expect errors to be reported do not check
the returned result. This change treats failures of the error handler
in that situation as fatal.

The default error handler already behaved that way. The others did not.

FixtureExpectsAllErrorsToMatchAPattern uses
CheckErrorsAgainstExpectations and it was safe to just make that func
treat any unmatching errors as fatal as all the existing usages are at
the end of test functions.

FixtureExpectsAtLeastOneErrorMatchingPattern uses the
FailIfNoMatchingErrors function which is used in a number of places
(including CheckErrorsAgainstExpectations) that do not want to treat
a test failure as fatal. So, that was modified to return false if no
matching error was found and the error handler treated that as fatal.

Bug: 181070625
Test: m nothing
Change-Id: I6e4df53f93250348bc050d4ff098134e6314ae30