docs: align incubator branding and packaging

[tisonkun]

Summary

• remove the stale Tokio-specific wording from the RwLock module documentation
• redesign the crate landing page around feature setup, an executable getting-started example, API discovery, and the runtime/blocking model
• remove migration content from crate-level docs and place the self-contained disclaimer at the end without blockquote indentation
• align every Markdown table in source for readable unrendered documentation
• identify standalone project docs as Apache Asyncband (Incubating) and link the packaged disclaimer
• add ASF trademark attribution to the README while retaining the podling-specific (Incubating) naming
• package MIGRATE.md and HISTORY.md with the crate so the README links resolve in the published artifact

Testing

• RUSTDOCFLAGS="--cfg docsrs -D warnings" cargo +nightly doc --all-features --no-deps
• cargo x lint
• cargo x test --no-capture
• cargo test --package asyncband --doc --all-features
• cargo package --package asyncband --locked --list
• cargo publish --package asyncband --locked --dry-run --allow-dirty