Parse query parameters before URL-decoding

[Copilot]

CCF decoded the full query string before splitting on &, so escaped ampersands were treated as parameter separators. For example, ?bar%26baz=tom%26jerry could not produce bar&baz = tom&jerry.

• Query handling

  • Preserve the raw query string on HttpRpcContext.
  • Split query parameters on raw & and =.
  • Decode each key/value component after splitting.

• Regression coverage

  • Added parser coverage for escaped & and = in parameter names and values.

GET /foo?bar%26baz=tom%26jerry

is now parsed as:

bar&baz = tom&jerry