Add skipped to the message for skipped tests in human reports

[mrodm]

Currently, if there are skipped tests (e.g. system or pipeline tests), there is no reference in the output about that test is skipped:

--- Test results for package: elastic_package_registry - START ---
╭──────────────────────────┬─────────────┬───────────┬───────────┬─────────────────────────────────────────────────────────────┬──────────────╮
│ PACKAGE                  │ DATA STREAM │ TEST TYPE │ TEST NAME │ RESULT                                                      │ TIME ELAPSED │
├──────────────────────────┼─────────────┼───────────┼───────────┼─────────────────────────────────────────────────────────────┼──────────────┤
│ elastic_package_registry │ metrics     │ system    │ default   │ test [https://github.com/elastic/integrations/issues/10904] │     30.268µs │
╰──────────────────────────┴─────────────┴───────────┴───────────┴─────────────────────────────────────────────────────────────┴──────────────╯
--- Test results for package: elastic_package_registry - END   ---

This PR adds SKIPPED: to the message with the reason and link. Example:

--- Test results for package: elastic_package_registry - START ---
╭──────────────────────────┬─────────────┬───────────┬───────────┬──────────────────────────────────────────────────────────────────────┬──────────────╮
│ PACKAGE                  │ DATA STREAM │ TEST TYPE │ TEST NAME │ RESULT                                                               │ TIME ELAPSED │
├──────────────────────────┼─────────────┼───────────┼───────────┼──────────────────────────────────────────────────────────────────────┼──────────────┤
│ elastic_package_registry │ metrics     │ system    │ default   │ SKIPPED: test [https://github.com/elastic/integrations/issues/10904] │     13.583µs │
╰──────────────────────────┴─────────────┴───────────┴───────────┴──────────────────────────────────────────────────────────────────────┴──────────────╯
--- Test results for package: elastic_package_registry - END   ---

This does not change the XML output (xUnit):

<?xml version="1.0" encoding="UTF-8"?>
<testsuites>
  <testsuite name="system" tests="1" skipped="1">
    <!--test suite for system tests-->
    <testcase name="system test: default" classname="elastic_package_registry.metrics" time="1.708e-05">
      <skipped message="test [https://github.com/elastic/integrations/issues/10904]"></skipped>
    </testcase>
  </testsuite>
</testsuites>

[elasticmachine]

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• Commit: 154a326

cc @mrodm