fix: clear ir cache when schema changes

Summary

• fix: clear ir cache when schema changes

See corresponding mr in sbroad: sbroad!322 (merged)

Ensure that

• New code is covered by tests
• API is documented
• Changelog is up to date
• (if Lua API changed) Lua API version is bumped in luamod.rs
• (if API docs changed) A follow-up doc issue is created in picodata/docs and linked here