Fix Postgres statements to remove information_schema query

[justiniso]

What does this PR do?

Removes a query to information_schema which requires different permissions from what our documentation grants. This change gets the required columns for querying pg_stat_statements directly from the view/function used.

Motivation

We ran into an issue with later versions of postgres on aurora where the pg_stat_statements view is owned by user rdsadmin and therefore the column names of the view are not exposed in information_schema.

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e) -- existing tests cover this change
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached