Refactor the `URI` class

[jviotti]

This is a master-issue for collecting requirements for improving the current URI class, reduce its dependency on uriparser, and prepare it for extracting it outside of this project:

• Add a URI::URI(std::istream &) constructor #800
• Add a [[nodiscard]] auto URI::userinfo() const -> std::optional<std::string_view> method #805
• Refactor URI::path() to return each component in the path as a std::span of std::string #807
• Add a URI::path_string() that returns the entire path as a string
• Extract the URI::escape and URI::unescape static methods into a separate component (uri/percent?):

auto encode_character(const char character, std::ostream &stream) -> void;
auto encode_string(std::istream &stream, std::ostream &output, const std::set<char> &whitelist) -> void;
auto encode_string(std::istream &stream, std::ostream &output) -> void;
auto decode_character(std::istream &stream, const std::uint64_t column = 0) -> char;
auto decode_string(std::istream &stream, std::ostream &output, const std::uint64_t column = 0) -> void;

• Add setter methods for every URI component #811
  • NOTE: After this one, revise the usage of URI across JSON Toolkit, as many workaround we do are for mutation, and can be simplified

On uriparser:

• Stop storing a UriUriA struct. Parse on the constructor and extract every component as a separate private member on the class, and operate on those from then on. If needed, construct back to UriUriA on the spot

[jviotti]

I'm doing more testing here: #2003