libs: remove unnecessary regex in pprof::symbolize

[erikgrinaker]

pprof::symbolize() used a regex to strip the Rust monomorphization suffix from generic methods. However, the backtrace crate can do this itself if formatted with the :# flag.

Also tighten up the code a bit.

[github-actions]

7546 tests run: 7173 passed, 0 failed, 373 skipped (full report)

---

Flaky tests (1)

Postgres 17

• test_migration_to_cold_secondary: release-x86-64-with-lfc

Code coverage* (full report)

• functions: 32.9% (8619 of 26193 functions)
• lines: 48.9% (72748 of 148856 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
147c172 at 2025-02-19T14:35:59.786Z :recycle:}