fix(log): Use a more compact relative-time format

This changes logged messages from
```
2023-08-23T01:01:59.922018Z DEBUG cargo::core::compiler::fingerprint: filesystem up-to-date "/home/epage/src/personal/dump"
```
To
```
   0.041729583s DEBUG cargo::core::compiler::fingerprint: filesystem up-to-date "/home/epage/src/personal/dump"
```
Benefits
- Less horizontal space taken up in boilerplate
- Easier to compare within a run

Downsides
- Harder to correlate with other processes, like with crates.io server
  operations

This gives us up to 4 digits for seconds which should be sufficient for
cargo build times.

We could make this more compact by dropping the digits of precision from
9 to 6 but that would require a custom Timer which might be a paint to
keep in sync between packages.

crates/xtask-bump-check/src/main.rs

@@ -20,6 +20,7 @@ fn setup_logger() {
     let env = tracing_subscriber::EnvFilter::from_env("CARGO_LOG");
 
     tracing_subscriber::fmt()
+        .with_timer(tracing_subscriber::fmt::time::Uptime::default())
         .with_ansi(std::io::IsTerminal::is_terminal(&std::io::stderr()))
         .with_writer(std::io::stderr)
         .with_env_filter(env)

src/bin/cargo/main.rs

@@ -41,6 +41,7 @@ fn setup_logger() {
     let env = tracing_subscriber::EnvFilter::from_env("CARGO_LOG");
 
     tracing_subscriber::fmt()
+        .with_timer(tracing_subscriber::fmt::time::Uptime::default())
         .with_ansi(std::io::IsTerminal::is_terminal(&std::io::stderr()))
         .with_writer(std::io::stderr)
         .with_env_filter(env)