feat: Add Cohesion stage keys and remove taggy

[julianajlk]

Some miscellaneous work for Red Ventures Cohesion event tracking work:

• Adding the Cohesion keys from edx-internal to distinguish between stage and prod.
• Removing taggy from the Cohesion snippet as it was causing a bad request error.
• Updating the PayPal click event.
• Updating the ConversionTracked event:
  This event on the ticket had category: "Order" but this is not actually an legitimate option from the schema. This is why I was consistently receiving a 400 bad request even though my payload had all the attributes.
  This is also an issue for checkout.edx.org -> appropriate team has been notified.

Note: the Cohesion config object is added via webpack.prod.config.js, which I found also runs in Stage. There is a webpack.dev-stage.config.js file, however, this is for local development with Stage variables.
I don’t have the context why there is no webpack for stage or a separate build for stage in MFEs at edX, I am hopping that adding these to edx-internal will suffice to have Stage/Prod keys.

edx-internal PR: https://github.com/edx/edx-internal/pull/11880

[christopappas]

looks like the var names are right and the stage keys are used here 👍