Misc fixes and refactors

[deedy5]

Summary:

This PR bundles several small improvements across the primp and primp-python crates:

• MSRV bump to 1.89.0
• Fix wasm32 build — gate h2-referencing code behind not(target_arch = "wasm32")
• Deflate consistency — add deflate field to BrowserSettings, default it true in all browser impersonators, wire it into apply_impersonation()
• Dep cleanup — replace once_cell::sync::Lazy with std::sync::LazyLock; remove unused h2, webpki-root-certs, typed-builder from primp-python
• Sync/async dedup — extract 6 identical methods from Client and AsyncClient into shared functions in client_builder.rs, removing ~40 lines of duplicate code
  Also includes earlier routine upstream merges, clippy fixes, and a CI fix already on the branch.