Update payload size when updating socket path

What does this PR do?

Description of the Change

When initialize sets socket_path, thus switching from udp to uds transport, update max_payload_size to use payloads of optimal size for the transport.

Alternate Designs

Possible Drawbacks

Verification Process

Additional Notes

Release Notes

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.

DataDog / datadogpy

Update payload size when updating socket path #807