Newrelic-lambda

* Fixes out-of-order output for threaded commands
* Pins `click` to `>=7.2.1` to include a fix for a file not found bug in Windows
* Fixes a bug where the subscription filter verification would override the filter pattern with the default

* Declares UTF-8 encoding to handle unicode errors 95
* `newrelic-lambda layers` and `newrelic-lambda subscriptions` commands now run in thread pool 95

* Updates the New Relic Layers API to `layers.newrelic-external.com`, deprecating `nr-layers.iopipe.com`

* Fixes an `newrelic-lambda integrations update` bug where an error would occur if there were no changes detected 92

- The newrelic-log-ingest function is now installed directly, rather than via a nested CloudFormation stack, which simplifies management.
- The upgrade process will migrate from a nested stack to an unnested stack.
- The upgrade CLI now preserves parameter values by default, so they don't need to be re-specified when you run the upgrade.

* Adds a `newrelic-lambda integrations update` command to update the log ingestion function 85
* Fixes bug where `newrelic-lambda subscriptions install` was returning an incomplete message for no change 86