Added deferrable transaction option to http batch queries

[jawj]

Problem

HTTP batch queries currently allow us to set the isolation level and read only, but not deferrable.

Summary of changes

Add support for deferrable.

Also, stop echoing read-only status in response headers unless true. Likewise only echo deferrable status in response headers if true.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

1588 tests run: 1513 passed, 0 failed, 75 skipped (full report)

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_{The comment gets automatically updated with the latest test results
73b9d7e at 2023-08-15T13:12:19.152Z :recycle:}