Enable 1.84 MSRV-aware resolution (#111)

## 🎟️ Tracking

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point to where this change is coming from. -->

## 📔 Objective

Rust 1.84.0 includes opt-in MSRV-aware version resolution, which ensures
`cargo update` won't try to update a package to a MSRV-incompatible
version.

Currently we have one package (`cargo-platform`) that can't be updated
to the latest version as it's not compatible with our MSRV. Enabling
MSRV-aware version resolution ensures that it won't be updated.

A test of it working:

```sh
# Running cargo update will update everything to the latest MSRV-compatible version
% cargo update
    Updating crates.io index
     Locking 31 packages to latest Rust 1.75 compatible versions
    Updating anyhow v1.0.94 -> v1.0.95
    Updating bitflags v2.6.0 -> v2.7.0
    Updating cc v1.2.4 -> v1.2.7
    <..... A few other packages ....>
note: pass `--verbose` to see 5 unchanged dependencies behind latest

# If we disable the MSRV-aware version resolution and run update again, we now get the MSRV incompatible update
% CARGO_RESOLVER_INCOMPATIBLE_RUST_VERSIONS=allow cargo update
    Updating crates.io index
     Locking 1 package to latest compatible version
    Updating cargo-platform v0.1.8 -> v0.1.9
note: pass `--verbose` to see 4 unchanged dependencies behind latest
```


Depends on #112 to fix
some lint issues


## ⏰ Reminders before review

- Contributor guidelines followed
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- Written new unit and / or integration tests where applicable
- Protected functional changes with optionality (feature flags)
- Used internationalization (i18n) for all UI strings
- CI builds passed
- Communicated to DevOps any deployment requirements
- Updated any necessary documentation (Confluence, contributing docs) or
informed the documentation
  team

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.cargo/config.toml

@@ -1,2 +1,5 @@
+[resolver]
+incompatible-rust-versions = "fallback"
+
 [target.'cfg(target_arch="aarch64")']
 rustflags = ["--cfg", "aes_armv8"]