tor-error: use `Display` for backtrace captured by `BugRepr`
Closes #1713 (closed).
Before:
2024-10-29T01:57:31Z ERROR arti: error: internal error (bug) at crates/arti/src/lib.rs:378:27: foo
Backtrace [{ fn: "tor_error::internal::ie_backtrace::capture", file: "./crates/tor-error/src/internal.rs", line: 21 }, { fn: "tor_error::internal::Bug::new_inner", file: "./crates/tor-error/src/internal.rs", line: 105 }, { fn: "tor_error::internal::Bug::new", file: "./crates/tor-error/src/internal.rs", line: 94 }, { fn: "arti::main_main", file: "./crates/arti/src/lib.rs", line: 378 }, ...
After:
2024-10-29T01:58:23Z ERROR arti: error: internal error (bug) at crates/arti/src/lib.rs:378:27: foo
0: tor_error::internal::ie_backtrace::capture
at ./crates/tor-error/src/internal.rs:21:27
1: tor_error::internal::Bug::new_inner
at ./crates/tor-error/src/internal.rs:105:24
2: tor_error::internal::Bug::new
at ./crates/tor-error/src/internal.rs:94:9
3: arti::main_main
at ./crates/arti/src/lib.rs:378:27
...