integrations: Update New Relic integration.

Newrelic has introduced a new update. This commit
updates the exisiting integration by adding support
for new types of payloads and cleaning up legacy
codes and fixtures.

Fixes #29729.

Co-authored-by: Pieter CK <pieterceka123@gmail.com>
Co-authored-by: Lauryn Menard <lauryn@zulip.com>

static/images/integrations/logos/newrelic.svg

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