feat: handle the migration to occurrence based deployments everywhere

[roleyfoley]

Intent of Change

• New feature (non-breaking change which adds functionality)

Description

• template and stack processing to use the district_type to split between account and segment
• Removes older stack handling which is no longer in use
• Removes support for product and multi deployments which aren't supported in the engine and will be added back in as required

Motivation and Context

This allows for occurrence based deployments to be completed in account and segment level districts to extend the control over how resources are deployed

How Has This Been Tested?

Tested locally

Related Changes

Prerequisite PRs:

• None

Dependent PRs:

• None

Consumer Actions:

• None

[ml019]

@roleyfoley I see the removal of some legacy file naming. Are we assuming all CMDBs have been upgraded such that these checks are no longer needed?