* Add manual trigger to Rust volume server release build workflow
When triggered manually via workflow_dispatch, binaries are uploaded as
downloadable workflow artifacts instead of release assets. On tag push
the existing release upload behavior is unchanged.
* Vendor OpenSSL for cross-compilation of Rust volume server
The aarch64-unknown-linux-gnu build fails because openssl-sys cannot
find OpenSSL via pkg-config when cross-compiling. Adding openssl with
the vendored feature builds OpenSSL from source, fixing the issue.
* Fix aarch64 cross-compilation: install libssl-dev:arm64 instead of vendoring OpenSSL
The vendored OpenSSL feature breaks the S3 tier unit test by altering
the TLS stack behavior. Instead, install the aarch64 OpenSSL dev
libraries and point the build at them via OPENSSL_DIR/LIB_DIR/INCLUDE_DIR.