build.mill files compiled by Scala 3 (com-lihaoyi#3369)

This is work in progress to fix
com-lihaoyi#3152

Numerous fixes were also needed to com-lihaoyi/mainargs,
com-lihaoyi/sourcecode, and com-lihaoyi/mill-moduledefs

With the current state, only 1 example/integration tests is still
failing:
- `integration.feature[plugin-classpath].local`

known TODOs:
- [x] Discover macro
- [x] Applicative macro
- [x] Caller macro
- [x] Cross.Factory macro
- [x] EnclosingClass macro
- [x] Task macros
- [x] Cacher macro
- [x] Moduledefs compiler plugin (override inferrence)
- [x] All core Mill modules compile with Scala 3.5.0
- [x] Fix Zinc reporter patch linenumbers of build scripts
- [x] Check that bytecode analyzers work with Scala 3
- [x] cleanup library dependency conflicts
- [x] Support new Scala 3 syntax in build.sc files
- [x] ~Fix BSP reporter linenumbers for build scripts~ (Zinc reporter
forwards to bsp)
- [ ] Cleanup compiler warnings for outdated syntax

known incompatibilities:
- [ ] can't use `ExplicitResultTypes` scalafix rule - need to upgrade
mill-scalafix
- [x] ~`Cross.scala` uses the new quoted type syntax which scalafmt
crashes on, (and version is frozen) so skip the file~ upgraded Scalafmt
so not skipped anymore
- [ ] skipping Mima currently due to 1000s of errors (perhaps we should
generate filters?)
- [ ] filtered one flaky test from `example.thirdparty[mockito]`
- [ ] filtered out `integration.feature[plugin-classpath]` due to third
party plugin dep

---------

Co-authored-by: Li Haoyi <[email protected]>

0.12.6 (com-lihaoyi#4296)

Update package.mill

0.12.4 changelog (com-lihaoyi#4142)

Prepare release 0.11.13

Prepare changelog for 0.12.2 (com-lihaoyi#3934)

CC @lefou FYI