[Feature][Shade] 3.0.0-fix — add calcite, upgrade janino, align scala with Spark - #12

Summary

This PR publishes updated shade artifacts to align with two upstream SeaTunnel PRs that have been merged into apache/seatunnel.

Upstream PRs

Changes

Root pom.xml:

• Add seatunnel-shade-calcite module
• Upgrade janino: 3.0.11 → 3.1.12
• Downgrade scala-compiler: 2.13.11 → 2.12.15 (binary: 2.13 → 2.12)
• Add calcite.version property (1.38.0)

New module: seatunnel-shade-calcite

Shades Apache Calcite 1.38.0 under org.apache.seatunnel.shade.*, relocating calcite-core and its transitive dependencies (avatica, janino, commons-codec, json-path, guava, checkerframework, etc.). Jackson and SLF4J are excluded since they are shaded separately.

README.md

Add project documentation covering module overview, build commands, partial release workflow, and post-release steps for the SeaTunnel project.

Rationale

• Calcite 1.38.0 — Required by the new Calcite SQL transform plugin (#11062) for standard SQL capabilities (SELECT, WHERE, CASE WHEN, UDFs, JSON extraction).
• Janino 3.1.12 — Calcite 1.38.0 depends on a newer janino version; the independent shade module is upgraded accordingly.
• Scala 2.12.15 — The scala-compiler was pinned to 2.13, but SeaTunnel's root build and Spark modules use 2.12, causing Scala signature version mismatch errors at runtime (#11117).

Verification

# Local build (skip GPG)
mvn -B -DskipTests -Drat.skip=true -Dgpg.skip=true \
  -pl seatunnel-shade-calcite,seatunnel-shade-janino,seatunnel-shade-scala-compiler \
  clean install

# Deploy to Apache repository
mvn -B -DskipTests -Drat.skip=true \
  -pl seatunnel-shade-calcite,seatunnel-shade-janino,seatunnel-shade-scala-compiler \
  clean deploy