[Qwix/Flax] Upgrade to Flax 0.12.0 + Qwix 0.1.4

[jrplatin]

Description

In this PR, I upgrade Qwix to 0.1.4 and upgrade Flax to 0.12.0. The only two major changes required to do so are:

• Disable eager sharding in Flax (to use the current paradigm)
• Change any instance of self.layers on a Flax model to be an nnx.List

Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.

[github-actions]

Description

Start with a short description of what the PR does and how this is a change from
the past.

The rest of the description includes relevant details and context, examples:

• why is this change being made,
• the problem being solved and any relevant context,
• why this is a good solution,
• some information about the specific implementation,
• shortcomings of the solution and possible future improvements.

If the change fixes a bug or a Github issue, please include a link, e.g.,:
FIXES: b/123456
FIXES: #123456

Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.

[py4]

Thanks! let's monitor the hourly graph after merging