fix: Fix compilation failures when not enabling default features

[sbernauer]

Needed for stackabletech/containerdebug#52

Problem

Some of our crates (notable stackable-operator) produce lot's of compilation errors when being pulled in with no default features, e.g.

stackable-operator = { git = "https://github.com/stackabletech/operator-rs", tag = "stackable-operator-0.106.2", default-features = false }

produces error: could not compile stackable-operator (lib) due to 237 previous errors

stackable-telemetry is even worse, as it is broken using default features:

stackable-telemetry = {git = "https://github.com/stackabletech/operator-rs", tag = "stackable-operator-0.106.2" }

causes

error[E0432]: unresolved import `clap`
  --> /home/sbernauer/.cargo/git/checkouts/operator-rs-10d25a4c6a1c49cf/f9b117c/crates/stackable-telemetry/src/tracing/mod.rs:12:5
   |
12 | use clap;
   |     ^^^^ no external crate `clap`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `stackable-telemetry` (lib) due to 1 previous error

Fix

This PR fixes the stackable-operator and stackable-telemetry by making mandatory features actually mandatory.
I also added pre-commit checks to prevent this from happening again.

With this fix I can now pull in exactly what I need in containerdebug:

stackable-shared = {git = "https://github.com/stackabletech/operator-rs", branch = "fix/crate-features" }
stackable-telemetry = {git = "https://github.com/stackabletech/operator-rs", branch = "fix/crate-features", features = ["clap"] }

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

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]

Blocking this for now, because I think this is the wrong approach to this issue.

[Techassi]

These changes unblock containerdebug to use default-features = false: https://github.com/stackabletech/operator-rs/tree/fix/features

I will do some research on how we can better detect this kind of stuff in the future. https://github.com/obi1kenobi/cargo-semver-checks might be the right tool for this job (and many others).

[sbernauer]

I quickly tried cargo test --no-default-features --package stackable-operator in your branch, looks like the problems aren't fixed yet. cargo test --no-default-features --package stackable-telemetry also doesn't work.
Also we should really have a CI action to prevent this in the future.

My PR also simplified the features quite a bit, it e.g. removed the clap feature from stackable-operator. Having it on stackable-telemetry makes sense, so I kept it, but stackable-operator always pulls in the clap crate, so from my perspective there is nothing to optimize for, it just complicates lot's of things. I also don't really like the idea that CLI flags depend on a rather technical Rust crate feature. operator-templating and the helm-charts don't know know and/or care about the Rust flag. They add a --eos-disabled (or similar), that works on 9 operators but fails on 3.

This PR solves all to me known problems and reduces complexity and is less error-prone. It also adds CI checks. So I personally would prefer to move along with it (happy to do some tweaks if needed).