Use Addressable::URI instead of stdlib URI for normalization

[casperisfine]

Alternative to #1005

Instead of trying to only escape the relevant fragments, this PR still applies escaping to all URLs, but does it with Addressable::URI, which is better at figuring out what needs to be escaped and what doesn't.

Example:

>> URI::Parser.new.escape(URI::Parser.new.escape('/foo bar'))
=> "/foo%2520bar"
>> Addressable::URI.parse(Addressable::URI.parse('/foo bar').normalize.to_s).normalize.to_s
=> "/foo%20bar"
>> Addressable::URI.parse('/foo[bar]').normalize.to_s
=> "/foo%5Bbar%5D"

It also have the advantage of using the same parser for every MRI versions which solves the parser discrepancies in #1005

@tarebyte what do you think?

[casperisfine]

The 2.4.3 build ran into what look like a MRI bug. I can't trigger a retry but I think it should pass.

[kytrinyx]

This looks good to me ⚡️

[tarebyte]

Thanks @casperisfine!

[casperisfine]

Thanks to you!

[tarebyte]

This has been released as part of https:/octokit/octokit.rb/releases/tag/v4.9.0