feat: add a mill build path for release

[tianrui-wei]

This commit adds a path for user to use mill to get the pre-packaged dependencies on Maven, instead of relying on git submodules. This is done for a couple of reasons.

1. Reduce the overhead of user getting started with chipyard
2. Easier for us to release tutorials, fewer hiccup on git submodules
3. Speed
4. Overall enables packages to be built without a big inter dependency net

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

Contributor Checklist:

• Did you set main as the base branch?
• Is this PR's title suitable for inclusion in the changelog and have you added a changelog:<topic> label?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• Did you mark the PR with a changelog: label?
• (If applicable) Did you update the conda .conda-lock.yml file if you updated the conda requirements file?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you add a test demonstrating the PR?

• (If applicable) Did you mark the PR as Please Backport?

[tianrui-wei]

Note that for users that develop RTL, they should still use the SBT path. This mill path is for RTL generation/running experiements only

[tianrui-wei]

Depends on ucb-bar/testchipip#153 and chipsalliance/rocket-chip-blocks#9

[jerryz123]

I don't think we are ready to support package-based integration of submodules yet for users, so I don't see why this needs to go into master.