Fix clippy lints for Rust 1.97

[fnando]

What

Fixes new clippy lint failures introduced by the Rust 1.97 upgrade so make check passes again. Removes redundant references in format arguments, drops a .to_string() call on a Display type, and inlines a format argument across 7 files.

Why

Rust 1.97 promotes several clippy lints (useless_borrows_in_formatting, to_string_in_format_args, uninlined_format_args) that broke the build under -D clippy::all. These are mechanical, no-behavior-change fixes to keep the lint gate green.

Known limitations

N/A

[Copilot]

Pull request overview

This PR updates several Rust CLI and test/support crates to satisfy newly promoted Clippy lints under Rust 1.97 (notably around redundant borrows in formatting, to_string() in format args, and uninlined format args), keeping make check green without intended behavior changes.

Changes:

• Removes redundant references (&...) in format arguments across multiple crates.
• Drops an unnecessary .to_string() in a formatting context for identity overwrite messaging.
• Uses Rust’s inline format argument syntax in a println! call.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cmd/soroban-cli/src/commands/tx/fetch/result.rs	Inlines a println! format arg to satisfy uninlined_format_args.
cmd/soroban-cli/src/commands/keys/generate.rs	Removes redundant borrow and .to_string() in overwrite identity message formatting.
cmd/soroban-cli/src/commands/keys/add.rs	Same formatting cleanup for overwrite identity message.
cmd/soroban-cli/src/commands/container/start.rs	Removes redundant borrow in a formatted “Starting network” info message.
cmd/crates/soroban-test/tests/it/build.rs	Removes redundant borrow in cargo_home.display() formatting used for path prefixing.
cmd/crates/soroban-test/src/lib.rs	Removes redundant borrows when formatting RPC header key/value into an env var string.
cmd/crates/soroban-spec-tools/src/contract.rs	Removes redundant borrow in a writeln! formatting argument for docs output.