[OSI-Converters] Begin parsing OSI SL documents

[QMalcolm]

Housekeeping

• I am a maintainer of dbt-core

Short description

OSI is beginning to define a open standard definition of how to define semantic layers. We support this effort. As such we want to support allowing OSI documents to be specified in dbt.

Acceptance criteria

• OSI documents are specifiable in /osi
• dbt-core can parse OSI into the manifest
• the produced semantic_manifest.json includes the OSI definitions
• SL objects can be defined both the native dbt way and the OSI way

Suggested Tests

• OSI documents end up in the manifest
• OSI documents end up in the semantic_manifest.json
• both dbt native and OSI SL definitions can both exist at the same time in a project

Impact to Other Teams

None

Will backports be required?

No

Context

No response