CLI - Replace clippy with a manual check

[bfops]

Description of Changes

We were apparently only using clippy to check for nonfunctional print statements (#1819).

This PR replaces our use of clippy (when building modules) with a manual check for disallowed print statements.

For me, this reduced the time of cargo clean && time spacetime build from 2m15s (with clippy) to 1m30s (without clippy).

API and ABI breaking changes

Not breaking.

Expected complexity level and risk

2

Future work

The other items in #1819.

Testing

• Manually added a println! to new module and observed that spacetime build produces an error:

$ spacetime build
info: component 'rust-std' for target 'wasm32-unknown-unknown' is up to date

Detected nonfunctional print statements:

./src/lib.rs:30:     println!("Hello world");

Error: Found 1 disallowed print statement(s).
These will not be printed from SpacetimeDB modules.
If you need to print something, use the `log` crate
and the `log::info!` macro instead.

[bfops]

should we be walking the whole project directory? As-is, this erroneously catches some printlns in BitCraft's build.rs. Should we be hardcoding to only look in src/...?

[bfops]

There does not appear to be a way to use e.g. cargo to list all the source files, as far as I can find. It looks like the best we could do is parse the output of the cargo build in order to figure out which files were involved.

[bfops]

Alternatively, we could add an extra argument that defaults to src/, e.g. --lint-path or something.