add: tool to sync aws-sdk-rust/next with smithy-rs (#1004)

* add: tool to sync aws-sdk-rust/next with smithy-rs

* fix: lint issues

* Update tools/smithy-rs-sync/src/main.rs

Co-authored-by: david-perez <d@vidp.dev>

* refactor: simplify commands by using a helper fn
update: use eprintln instead of println
update: note number of successfully mirrored commits in success message
update: use fs::read_to_string
update: use .display() instead of .to_string_lossy() for displaying paths
update: ensure absolute paths in fn copy_sdk
update: use iters instead of for loop in fn commits_to_be_applied

* add: fn for deleting files/ folders not in allowlist

* add: missing copyright header
remove: TODO

* refactor: handwritten to work with gitignore
add: check we're not generating files marked as handwritten
add: fn to list handwritten files
add: test for find_handwritten_files_and_folders
fix: clippy lint
add: timer for SDK cleanout
remove: once_cell dep
sort: deps in Cargo.toml

* fix: set smithyrs-githash per mirror commit
update: set bot as committer

* refactor: HandwrittenFiles to return iters

* add: Russell's error hint

Co-authored-by: david-perez <d@vidp.dev>
Co-authored-by: AWS SDK Rust Bot <aws-sdk-rust-primary@amazon.com>