Allow tests to be disabled

[ycombinator]

In elastic/integrations#514, @adriansr had to disable some packages' system tests in order to make progress on his feature. To do this, he had to remove the system test configuration files entirely because that is the only way to disable tests at the moment.

Instead, it would be nice if the configuration files accepted a skip or similar field which, if present, would skip the test. Further, the value of this field could be an arbitrary string representing the reason for skipping/disabling the test. Finally, this capability could be applied not just to system tests but also other types of tests.

• package-spec changes to allow skip field: Add field to allow skipping of tests package-spec#105
• elastic-package changes to respect skip field in test runners: Add ability to skip tests #221

[ycombinator]

Resolved via elastic/package-spec#105 and #221.