build: package separate runtime and CLI artifacts

[omer-cengel]

Summary

Split sqlcj into a small application runtime artifact and a dependency-inclusive executable CLI so generated applications do not inherit compiler dependencies.

Changes

• Convert the root project into a shared-version Maven reactor.
• Package the four JDBC runtime types in dev.sqlcj:sqlcj-runtime with no main dependencies.
• Package the compiler and command-line entry point in dev.sqlcj:sqlcj-cli.
• Produce an executable shaded CLI JAR with preserved implementation-version metadata.
• Relocate existing production sources and tests unchanged into their owning modules.

Scope and non-goals

This change preserves Java packages, generated and runtime APIs, configuration discovery, diagnostics, exit codes, and compiler behavior. It does not add user documentation, publication configuration, release automation, signing, checksums, build-system plugins, or SQL/runtime features.