feat(github): replace adapter-based project with Integration Model CRUD workflows

[michaelelrom]

Summary

• Trims github_rest_api-latest.json from 320 to 248 curated operations, dropping legacy /teams/{team_id} endpoints (superseded by org+slug equivalents), emoji reactions (thin long tail across 6 resource types), and the most granular branch-protection sub-resources (enforce_admins, required_signatures, restrictions by app/team/user) — core protection CRUD is retained.
• Fixes the spec's servers entry to a static URL; Itential Platform Integration Models require a static server URL rather than OpenAPI server variables, so Enterprise Server host/base_path are now configured per-instance instead (documented in the README, same pattern as GitLab's SaaS/self-hosted split).
• Replaces the old 4-workflow GitHub Adapter Studio Project with 251 CRUD workflows across 16 folders, backed by the GitHub REST API:latest Integration Model.
• Nine generic resource names (Organization, Branch, Commit, Commit Comment, Repository File, Release, Deployment, Environment, Tag) are prefixed with GitHub to avoid collisions with identically-named workflows already published for other products (workflow names are unique platform-wide, not per-project).
• Rewrites GitHub/README.md to document the Integration Model-only configuration and the new folder structure, dropping the legacy Adapter instructions.

Test plan

• All 251 workflows created and schema-validated against a running Itential Platform instance
• Get Authenticated User and List Organization Members executed against a real GitHub account and confirmed returning live data
• Remaining workflows not individually executed