test: allow phpunit 10

[phil-davis]

Try this in cache first just to see what happens.

1. phpunit 10 does not accept abstract classes for test code, ending with "Test".

There was 1 PHPUnit test runner warning:

1) Class Sabre\Cache\AbstractCacheTest declared in /home/runner/work/cache/cache/tests/Cache/AbstractCacheTest.php is abstract

I renamed AbstractCacheTest to AbstractCacheTestClass and that stopped the warning.

2. In PHP 8.4 we were running phpunit and asking to produce test coverage data, but hadn't specified the coverage driver "pcov". PHPunit 9 had not made that a failure, but PHPunit 10 fails (correctly) in that case. I fixed it.

PHPunit 10 also gives the message:

There was 1 PHPUnit test runner deprecation:

1) Your XML configuration validates against a deprecated schema. Migrate your XML configuration using "--migrate-configuration"!

That does not fail the test pipeline. We can't do anything about that, because we need to have the phpunit XML config in the version 9 format so that we can use it on PHP 7.4. An alternative would be to update it, and put the old phpunit XML in a different file that we use when running PHPunit 9. That seems to complex/tricky.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 98.75%. Comparing base (ff649f7) to head (ba64554). :warning: Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #72   +/-   ##
=========================================
  Coverage     98.75%   98.75%           
  Complexity       89       89           
=========================================
  Files             4        4           
  Lines           160      161    +1     
=========================================
+ Hits            158      159    +1     
  Misses            2        2           

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