[AMLII-2170] fix removed/renamed function flush

[andrewqian2001datadog]

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What does this PR do?

Renaming the flush function caused a breaking change

Issue 1, 2

Description of the Change

Add the flush function back to the api and revert renaming of another global variable.

Verification Process

Unit tests.

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• 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 one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
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