Add clippy check for overflowing arithmetic, fix existing cases

[Br1ght0ne]

Fix #1238.

Uses [workspace.lints] to set uniform linting configuration for all our packages (see [package.lints]).

Uses checked_ where a Result is returned from the function already, and saturating_sub where a value of 0 on overflow makes sense (to avoid refactoring Result into most of the codebase).

Checklist

• I have linked to any relevant issues.
• I have updated the documentation.
• I have added tests that prove my fix is effective or that my feature works.
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[iqdecay]

I'm not 100% convinced by the approach, we can discuss it on Slack.

[iqdecay]

Seeing all these saturating adds here makes me question if this is a good idea or not, I could see a transaction being crafted to trigger these saturating adds and resulting in, at best an invalid transaction, at worse a malicious one.