chore(envoy update): update Envoy submodule and package URL to v2.2.1

[Jing-ze]

Ⅰ. Describe what this PR did

• Updated ENVOY_PACKAGE_URL_PATTERN to point to v2.2.1 release package.
• update the Envoy git submodule to the commit corresponding to 1.36.4

Ⅱ. Does this pull request fix one issue?

No. This PR is a dependency/chore update and does not directly fix a specific tracked issue.

Ⅲ. Why don't you add test cases (unit test/integration test)?

No functional logic change in Higress itself; only Envoy submodule and package URL are updated.

Ⅳ. Describe how to verify it

• Build Higress image/binary with the updated Envoy: Ensure the build completes successfully using the new Envoy package.
• Run existing test suite / e2e scenarios: Confirm that core gateway functionality (routing, TLS, plugins) works as before.

Ⅴ. Special notes for reviews

Ⅵ. AI Coding Tool Usage Checklist (if applicable)

Please check all applicable items:

• For new standalone features (e.g., new wasm plugin or golang-filter plugin):

  • I have created a design/ directory in the plugin folder
  • I have added the design document to the design/ directory
  • I have included the AI Coding summary below

• For regular updates/changes (not new plugins):

  • [] I have provided the prompts/instructions I gave to the AI Coding tool below
  • I have included the AI Coding summary below

AI Coding Prompts (for regular updates)

AI Coding Summary