New @deno/kv npm package.

[johnspurlock-skymethod]

New @deno/kv NPM package, built from code contributed from skymethod/kv-connect-kit.

• remote client, implements kv connect protocol, including v3 (watch), runs in any JS runtime
• new node-specific sqlite implementation using a single platform-specific napi module, sharing existing denokv sqlite backend code
• in-memory implementation for testing, runs in any JS runtime
• full-fidelity v8 value serialization, using node's v8 module
• single openKv convenience export, chooses implementation based on path (if http/https -> remote, if blank/empty -> in-memory, else sqlite)
• code lives in new top-level npm directory
• napi module lives in npm/napi, leverages NAPI-RS framework to translate Rust -> NAPI
• script source lives in npm/src, includes end to end tests for the various implementations using deno test
• automated build process to produce/publish root @deno/kv + 4 arch-specific native subpackages