chore(tracing-actix-web): move examples to actix/examples

[robjtede]

PR Type

Refactor

Overview

Move the three tracing-actix-web example applications to actix/examples in actix/examples#1423. Remove their workspace entries and unused lockfile dependencies, and point the crate documentation and README to the new locations.

Merge the companion examples PR first so the documentation links resolve.

PR Checklist

• Tests for the changes have been added / updated. Not applicable: this change removes relocated examples and updates links.
• Documentation comments have been added / updated.
• A changelog entry has been made for the appropriate packages. Not applicable: no library behavior or API changes.
• Format code with the nightly rustfmt (cargo +nightly fmt).

Validation

• cargo check -p tracing-actix-web --lib --offline
• cargo +nightly fmt -p tracing-actix-web -- --check
• Prettier check for tracing-actix-web/README.md.

The crate check passed with existing manifest lint-name deprecation warnings.