feat(node): implement HTTP/2 settings API (getDefaultSettings, getPackedSettings, getUnpackedSettings)

[dive2tech]

Summary

Implements the Node.js-compatible HTTP/2 settings API for node:http2:

• http2.getDefaultSettings() – Returns default HTTP/2 settings (RFC 7540 + Node.js defaults).
• http2.getPackedSettings(settings) – Packs a settings object into a Buffer for the HTTP2-Settings header (6 bytes per setting: 16-bit ID + 32-bit value, big-endian).
• http2.getUnpackedSettings(buffer) – Unpacks a Buffer or TypedArray of packed settings into an object.

Changes

• New: ext/node/polyfills/internal/http2/settings.ts – Encoding/decoding and validation per RFC 7540; supports known settings (headerTableSize, enablePush, maxConcurrentStreams, initialWindowSize, maxFrameSize, maxHeaderListSize, enableConnectProtocol) and numeric IDs for unknown settings.
• Updated: ext/node/polyfills/http2.ts – Replaces notImplemented stubs with the new implementation.
• Updated: tools/core_import_map.json – Registers the new internal settings module.
• New: tests/unit_node/http2_settings_test.ts – Tests for defaults, roundtrip, validation (enablePush 0/1, maxFrameSize bounds, initialWindowSize max, etc.), invalid inputs, and packed format.

Compatibility

• Defaults and packed format align with Node.js and RFC 7540.
• Validation (non-negative integers, enablePush/enableConnectProtocol 0 or 1, maxFrameSize 16384–16777215, initialWindowSize ≤ 2^31-1) matches Node behavior.

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

Thanks for the PR, but there's little chance we will merge it. We are already working on node:http2 support in #30955, which is a multi-month project and would cause conflicts.

Next time, please open an issue first to discuss if someone else has already tackled this work.

[dive2tech]

Hi @bartlomieju,

I’ve added the HTTP/2 settings.
When you have a moment, please take a look.

If everything looks good, feel free to merge it, or let me know if I should close it.

Thanks!