This implements a new class, QueryEncoder, that provides
methods for encoding keys and values of query parameter.
The encoder encodes with encodeURIComponent, and then
decodes a whitelist of allowed characters back to their
unencoded form.
BREAKING CHANGE:
The changes to Http's URLSearchParams serialization now
prevent encoding of these characters inside query parameters
which were previously converted to percent-encoded values:
@ : $ , ; + ; ? /
The default encoding behavior can be overridden by extending
QueryEncoder, as documented in the URLSearchParams service.
Fixes#9348
1620426393