[FLINK-9074] [e2e] Add e2e for resuming from externalized checkpoints

[tzulitai]

What is the purpose of the change

This PR adds an end-to-end test for resuming from externalized, retained checkpoints.

The test does the following:

• Runs the general purpose DataStream job, with externalized checkpoints enabled
• Waits until the job has at least 1 completed checkpoints, AND has processed at least 200 records
• Cancel the job
• Make sure that there is exactly 1 externalized checkpoint available
• Restore from that, wait for another 200 records to be processed to verify that exactly-once isn't violated

Brief change log

• Allow general purpose job to be configured for externalized checkpoints
• Add new e2e test script test_resume_externalized_checkpoint.sh

Verifying this change

This PR adds a new test, test_resume_externalized_checkpoint.sh.

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[fhueske]

thanks for the PR @tzulitai.
The new e2e tests passed on my machine. The changes look good as well.
+1 to merge

[tzulitai]

Thanks a lot for the review @fhueske.
Will merge this!