Revert mill init bloated dependencies and fix SpringBootModule reflection (-parameters)

[vaslabs]

Fixes #7197

On the broken examples mentioned in the reverting PR see:

• mill init Bloated build files in SpringBoot migration #7197 (comment)
• mill init Bloated build files in SpringBoot migration #7197 (comment)

Also fixes #7268 by having a default -parameters for javacOptions in SpringBootModule

> git clone git@github.com:in28minutes/spring-boot-examples.git
> cd spring-boot-examples/spring-boot-rest-services-with-unit-and-integration-tests
> mill --version
Mill Build Tool version 1.1.6-112-620712-DIRTY2ee0760
java.version: 21.0.2
java.vendor: Oracle Corporation
java.home: /home/vnicolaou/.sdkman/candidates/java/21.0.2-open
file.encoding: UTF-8
os.name: Linux
os.version: 7.0.11-200.fc44.x86_64
os.arch: amd64

> mill init
1] init
14] mill.init.InitMavenModule/init
converting Maven build
writing build.mill.yaml
14] formatting Mill build files
14] Formatting 1 Scala sources
parsed config (v3.8.5): ../mill-workspace/out/mill.init.InitMavenModule/buildGenScalafmtConfig.dest/.scalafmt.conf
file excluded: ../mill-workspace/build.mill.yaml
14] init completed, run "mill resolve _" to list available tasks
1/1, SUCCESS] mill init 1s

> mill test
124] Test com.in28minutes.springboot.controller.StudentControllerIT#addCourse() finished, took 0.052s
124] Test com.in28minutes.springboot.controller.StudentControllerIT#testRetrieveStudentCourse() started
124] Test com.in28minutes.springboot.controller.StudentControllerIT#testRetrieveStudentCourse() finished, took 0.009s
124] 2026-06-13T15:16:10.568+03:00  INFO 43021 --- [           main] [                                                 ] o.s.boot.tomcat.GracefulShutdown         : Commencing graceful shutdown. Waiting for active requests to complete
124] 2026-06-13T15:16:10.570+03:00  INFO 43021 --- [tomcat-shutdown] [                                                 ] o.s.boot.tomcat.GracefulShutdown         : Graceful shutdown complete
124] Test com.in28minutes.springboot.controller.StudentControllerIT finished, took 0.358s
124] Test junit-jupiter finished, took 0.361s
124] Test run finished: 0 failed, 0 ignored, 2 total, 0.361s
124/124, SUCCESS] mill test 7s

Other

Also updated the spring boot docs with a few lines to mention some features SpringBootModule brings out of the box (including the new addition with the -parameters compiler option)

[vaslabs]

@souvlakias please check I haven't accidentally reverted your quarkus work or anything else

[souvlakias]

@souvlakias please check I haven't accidentally reverted your quarkus work or anything else

All good 👍