Update `_filter_headers` to check data collection settings when available

[ericapisani]

_filter_headers handles the scrubbing of sensitive data that lives within the request headers, and is used across various integrations.

Update this function to respect the settings within the data collection object when it's available.

We may want to also consider as part of this extending the functionality of this function to also support response headers. Currently we don't apply data scrubbing on response headers and will need to do so in order to support the data collection spec fully.

[linear-code]

PY-2584