TeamCity: port build configs to in-repo Kotlin DSL

[sergej-koscejev]

Summary

• Moves the mps-gradle-plugin and git-based-versioning TeamCity build configurations from the TC UI into .teamcity/settings.kts (Kotlin DSL).
• Keeps full parity with the current v1.x behavior: the plugin build runs setTeamCityBuildNumber build and then publish; git-based-versioning runs :git-based-versioning:build :git-based-versioning:publish.
• Pom layout mirrors mbeddr/publish-mps-prereleases/.teamcity/pom.xml — parent org.jetbrains.teamcity:configs-dsl-kotlin-parent:1.0-SNAPSHOT via https://mps.builds.itemis.cloud/app/dsl-plugins-repository.
• Pairs with the master PR (same change, without the Publish step) so master can later diverge for 3.0.0: task-type interfaces, Gradle 9, drop legacy plugins #177 (selective on-demand publishing of included builds) without touching v1.x.

Handover checklist for TeamCity

These steps apply once both this PR and the master PR are merged:

1. On the newly-created Mbeddr_Tooling_MpsGradlePlugin subproject in TeamCity, switch Versioned Settings synchronizationMode from useParentProjectSettings to Synchronization enabled. Point at the existing VCS root (Mbeddr_Tooling_MpsGradlePlugin, which targets https://github.com/mbeddr/mps-gradle-plugin). Turn on "Use settings from the branch being built".
2. TC imports the DSL; two new build configs appear. Trigger each manually on v1.x and master and compare against the last legacy runs (build log, ##teamcity[buildNumber '…'], artifact list, GitHub commit status).
3. After parity, archive or delete the two legacy configs (Mbeddr2_Mbeddr_Gradle_MpsGradlePlugin, Mbeddr2_Mbeddr_Gradle_GitBasedVersioning).

Note: the DSL reuses the inherited %system.github.token% for the commit-status publisher. Worth confirming this is the same token the current legacy config's per-build-config secure:github_access_token holds; if not, we'll need a project-scoped credentials entry before archiving the old config.

Test plan

• cd .teamcity && mvn teamcity-configs:generate produces XML under target/generated-configs/ matching the live configs' semantics.
• After TC sync on v1.x, plugin build runs Build + Publish, publishes a maven-mps-snapshots artifact, GitHub commit status updates.
• After TC sync on v1.x, git-based-versioning build runs its single step successfully (triggered manually or via dependency).
• No "settings differ from VCS" warnings on the new project after first sync.

🤖 Generated with Claude Code

[nkoester]

I've reviewed the changes in this PR. Sergej and I had a call on March 23rd to discuss the context, and we've covered all the $3.0$-related updates. Thanks for your work! LGTM!