Gainsight PX Device Mode new integration

[gs-nwolfe]

What are the changes introduced in this PR?

New Gainsight PX device mode integration

What is the related Linear task?

n/a

Please explain the objectives of your changes below

The intention is to allow customers to load the Gainsight PX javascript SDK in the browser and send events directly to Gainsight PX from the client side. This new integration will likely be used more than the existing home-grown Gainsight PX integration that uses the REST API to send events from server-to-server.

To avoid conflicts with the existing Gainsight PX integration, I used the name of "GAINSIGHT_PX_BROWSER".
There are corresponding PR's to the sdk-js and docs repos.
Docs PR: rudderlabs/rudderstack-docs#1193

Any changes to existing capabilities/behaviour, mention the reason & what are the changes ?

N/A

Any new dependencies introduced with this change?

N/A

Any new checks got introduced or modified in test suites. Please explain the changes.

N/A

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Developer checklist

• My code follows the style guidelines of this project

• No breaking changes are being introduced.

• All related docs linked with the PR?

• All changes manually tested?

• Any documentation changes needed with this change?

• I have executed schemaGenerator tests and updated schema if needed

• Are sensitive fields marked as secret in definition config?

• [n/a] My test cases and placeholders use only masked/sample values for sensitive fields

• Is the PR limited to 10 file changes & one task?

Reviewer checklist

• Is the type of change in the PR title appropriate as per the changes?

• Verified that there are no credentials or confidential data exposed with the changes.