document the default value of the form's compound option
add the action option and the method option to the introductionary table, remove doubled include of them
fix the order of the options in the table to match their order below
minor #3789 [Reference][Forms] Improvements to the form type (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Reference][Forms] Improvements to the form type

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Commits
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8a6feb8 fix the order of the options in the table to match their order below
8e7ebf5 add the action option and the method option to the introductionary table, remove doubled include of them
f6a6566 document the default value of the form's compound option