chore: modularize build logic, move model classes

--Minify build container image, upgrade gradle and java deps; add instructions for building on non-native platforms (relevant for building x64 images on macOS arm64)
--Update ci/cd pipeline so that it uses digest pinning instead of tags (protects against malicious docker image updates)
--Configure formatting tool (spotless) to use latest stable ktlint version
--Update dependency versions in lib catalog,
--Add abstract classes which extend TemerityFunSpec and perform pre-test client config, removing test boilerplate
--Rename user API functions for clarity
--Formatting