Run Cargo clippy and fmt in CI

[edmorley]

Since we should always be running these in CI for all projects that use Rust.

The job was copied from that run here:
https://github.com/heroku/heroku-java-metrics-agent/blob/86dd6bf68d3cafdecbc0b281f2a4f54a00c41371/.github/workflows/ci.yml#L82-L98

GUS-W-18062768.

[edmorley]

Clippy is currently failing with:

error: docs for function which may panic missing `# Panics` section
  --> src/lib.rs:37:1
   |
37 | pub fn heroku_jvm_application_deployer_jar_path() -> PathBuf {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: first possible panic found here
  --> src/lib.rs:42:22
   |
42 |     for dir_entry in std::fs::read_dir(maven_target_dir).unwrap() {
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc
   = note: `-D clippy::missing-panics-doc` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::missing_panics_doc)]`

error: case-sensitive file extension comparison
  --> src/lib.rs:46:72
   |
46 |         if file_name.starts_with("heroku-jvm-application-deployer") && file_name.ends_with(".jar") {
   |                                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a case-insensitive comparison instead
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#case_sensitive_file_extension_comparisons
   = note: `-D clippy::case-sensitive-file-extension-comparisons` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::case_sensitive_file_extension_comparisons)]`
help: use std::path::Path
   |
46 ~         if file_name.starts_with("heroku-jvm-application-deployer") && std::path::Path::new(&file_name)
47 +             .extension()
48 ~             .map_or(false, |ext| ext.eq_ignore_ascii_case("jar")) {
   |

error: docs for function which may panic missing `# Panics` section
  --> src/lib.rs:55:1
   |
55 | pub fn http_get_expect_200(url: &str) -> String {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: first possible panic found here
  --> src/lib.rs:56:5
   |
56 | /     thread_sleep_backoff(10, Duration::from_secs(1), Duration::from_secs(30), || {
57 | |         ureq::get(url).call()
58 | |     })
59 | |     .expect("")
60 | |     .into_string()
61 | |     .expect("")
   | |_______________^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc

error: docs for function which may panic missing `# Panics` section
  --> src/lib.rs:65:1
   |
65 | pub fn create_heroku_app(path: &Path, space: Option<&str>) -> HerokuAppCreateResult {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: first possible panic found here
  --> src/lib.rs:79:5
   |
79 |     serde_json::from_slice::<HerokuAppCreateResult>(&output.stdout).unwrap()
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc

error: docs for function which may panic missing `# Panics` section
   --> src/lib.rs:114:1
    |
114 | pub fn run_command(command: &mut Command, error: &str, suppress_output: bool) -> Output {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: first possible panic found here
   --> src/lib.rs:115:18
    |
115 |       let output = if suppress_output {
    |  __________________^
116 | |         command.output()
117 | |     } else {
118 | |         command.output_and_write_streams(stdout(), stderr())
119 | |     }
120 | |     .expect("");
    | |_______________^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc

error: docs for function which may panic missing `# Panics` section
   --> src/lib.rs:137:1
    |
137 | pub fn prepare_fixture(name: &str) -> PathBuf {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: first possible panic found here
   --> src/lib.rs:138:20
    |
138 |     let temp_dir = tempfile::tempdir().expect("").into_path();
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc