chore: Bump Rust version to 1.87.0 and workflow actions

[sbernauer]

Description

Part of #1018

No changelog entry, as this should only be repo-internal changes.
Lot's of new clippy lints to fix.

Definition of Done Checklist

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Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added

[Techassi]

I'm not a huge fan of all these Boxes, but oh well, what can you do. This can only be fixed upstream (if possible at all). I would also like us to bump to Rust 1.88.0 instead.

I left one comment requesting changes. Everything else looks good.

[sbernauer]

I would also like us to bump to Rust 1.88.0 instead.

I would prefer that as well, but nixpkgs unstable is currently on 1.87, which is used in make run-dev.
I personally think it's not worth the extra effort to fiddle around with the niv/nixpkgs/crate2nix/whatnot setup.
We can always bump to 1.88 as needed later, unrelated to the SDP release cycle.

We already have a discussion about this in https://stackable-workspace.slack.com/archives/C02FZ581UCD/p1752043094194079?thread_ts=1752042485.505039&cid=C02FZ581UCD

[Techassi]

@NickLarsenNZ and I decided to move forward with Fenix after the 25.7.0 release. Once that transition is done, we can always bump to the latest available stable Rust version without the need to wait for upstream Nixpkgs.

For now, we can keep it at 1.87.0.

[sbernauer]

Sure, works for me!

[Techassi]

Approved as is, but we should invest some time on reducing the error sizes down the line. Introducing these Boxes all over the place makes the code harder to read and maintain.