Tilde should not be escaped as per RFC3986

[y4m4p]

Hi, first time contributing so sorry if I'm missing anything!

Issue

• https://bugs.ruby-lang.org/issues/20690

Heads up

This might be a breaking change, since some server-client setup might rely on ~ being encoded to %7E for whatever reason.
But since this is an RFC offense, the proposed implementation should be the way to go and must be enforced for future usage in web interactive applications and such.

Decoding ~ must remain the same, we just don't want to encode ~.

Details

This PR's change follows other escaping methods in core Ruby, such as CGI.escape, ERB::Util.url_encode (which actually just calls CGI.escapeURIComponent inside).

# URI (current implementation)
irb(main):002:0> require 'uri'
=> true
irb(main):004:0> URI.encode_www_form_component("ruby~test")
=> "ruby%7Etest"

# CGI
irb(main):001:0> require 'cgi'
=> true
irb(main):003:0> CGI.escape("ruby~test")
=> "ruby~test"

# ERB
irb(main):009:0> require 'erb'
=> true
irb(main):012:0> ERB::Util.url_encode("ruby~test")
=> "ruby~test"

# Webrick
# needs webrick gem installed
[3] pry(main)> require 'webrick'
=> true
[4] pry(main)> WEBrick::HTTPUtils.escape_form("ruby~test")
=> "ruby~test"
[5] pry(main)> WEBrick::HTTPUtils.escape("ruby~test")
=> "ruby~test"

[hsbt]

I'm closing this by https://bugs.ruby-lang.org/issues/20690#note-2