[threadstats] Ensure ThreadStats and DogStatsd event() signatures match

[sgnn7]

What does this PR do?

Changes text positional arg in threadstats to message

Closes: #707

Description of the Change

Since 0.43, statsd has renamed a positional argument text to
message. When a user is invoking the API of this method with kwargs for named
parameters it no longer can be used to swap seamlessly between
ThreadStats and DogStatsd. This change ensures that both positional args
have the same names.

For more info: #707 (comment)

Alternate Designs

Possible Drawbacks

Potentially a breaking change for users of ThreadStats if they use event() with
named positional args. Release notes are updated to make that clear.

Verification Process

CI/CD tests

Additional Notes

Release Notes

• ThreadStats().event() and DogStatsd.event() now both use message instead of text as the name of the second positional argument

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.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.

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