Add data-test-subj attributes for License Management UI

[LeeDr]

Describe the feature: Please add the following data-test-subj attributes to the License Management UI to enable functional testing.

Describe a specific use case for the feature: I'm working on these tests in a separate repo where the tests run in VMs and I can move the clock around for expiring licenses and can restore a snapshot to go through different scenarios, so we may not see many of these tests in this repo.

I'll suggest data-test-subj values but certainly open for discussion.

1. data-test-subj="licenseText" We need to be able to check that this text shows the expected license
   

2. data-test-subj="licenseSubText" would be nice to also be able to check this subtext which shows when/if the license will expire
   

3. data-test-subj="updateLicenseButton"
   

4. data-test-subj="startTrialButton"
   

5. data-test-subj="revertToBasicButton"
   

6. data-test-subj="extendTrialButton"
   

7. data-test-subj="licenseFileUploadLink"
   

8. data-test-subj="licenseCancelUploadButton" and data-test-subj="licenseUploadButton"
   

9. These buttons already have data-test-subj's
   

10. data-test-subj="licenseUploadErrorText
    

11. These already have generic data-test-subjs confirmModalCancelButton and confirmModalConfirmButton
    

[bmcconaghy]

@LeeDr #7 is in EUI and not in control of the code for license management. I think selecting on input of type file should work for that as that is the only file input present.

[LeeDr]

@bmcconaghy I'm OK with that on #7. And/or I can file an issue in EUI to get a data-test-subj added.