Fix custom Databricks-prefixed plugin UI

[Bionic711]

Motivation & Context

Custom plugin types with Databricks-prefixed names, such as databricks_table_dscmo, could be treated like built-in Databricks actions during action type discovery or visual rendering. This made custom plugins appear to load Databricks-specific UI behavior instead of the standard plugin UI.

This change keeps only the exact built-in Databricks action types on the Databricks path and lets custom Databricks-prefixed plugin types use the standard plugin path.

Description & Review Guide

• What are the major changes?

  • Added exact built-in Databricks type classification for databricks and legacy databricks_table.
  • Updated action type discovery to avoid broad databricks substring matching.
  • Updated the shared workspace action icon helper so custom Databricks-prefixed types do not inherit the Databricks icon treatment.
  • Added a scaffolded functional regression test that creates a temporary databricks_table_dscmo plugin, definition file, and schema files, then verifies discovery and settings merge stay on the standard path.
  • Added fix documentation and release notes for version 0.250.103.

• What is the impact of these changes?

  • Built-in databricks and databricks_table actions continue to use the Databricks-specific path.
  • Custom types such as databricks_table_dscmo use standard plugin discovery, settings merge, and visual treatment.
  • No migration is required for existing action records.

• What do you want reviewers to focus on?

  • Confirm the exact-match Databricks classification preserves legacy databricks_table compatibility while preventing custom suffix types from being reclassified.
  • Review the scaffolded regression test approach, especially the temporary plugin/schema setup and cleanup behavior.

Related Issue

Fixes #1124

Contribution Checklist

• This change includes tests or updates existing tests.
• This change includes documentation or release notes where appropriate.
• This is not a breaking change.