Remove URL stubs for 0.5.0

[ekrich]

This PR removes java.net.URL and friends and also java.net.URI.toURL. It is important to do these removals as soon as possible in these breaking releases to give downstream application a chance to adapt. Also, removing them now with no deprecation cycle is better to avoid future people from relying on the code while we have less adoption and more motivated adopters.

URL stubs were added to support https://github.com/ekrich/sconfig which is an important dependency for a Scala Native version of scalafmt. Other libraries may have been relying on them too.

Because URL is basically a full HTTP client library, it is non-trivial to implement. It is not implemented in Scala.js because it is not possible due to concurrent DNS lookups and Scala Native also supports a single threaded runtime, so we should not add it to the base system.

A release file was added using the last major release as a template. This was needed to capture the details.

[ekrich]

@WojciechMazur This is ready for review.

[LeeTibbert]

Eric, what offering did you give to multiarch builds?
They are all green for you and have been failing
for me for months.

You must be leading a more virtuous life than I and
the Universe/Multiverse is rewarding it.

[LeeTibbert]

The changelog herein is a much better starting point. Thanks Eric.
After this PR is merged, I will rebase PR #2783 on this.

Do you have thoughts of where you would like to see a "Deprecations" section?
You seem to have a rhythm here and I do not want to disrupt it.

[ekrich]

I just copied the 0.4.0 file because it was the last major release with lots of changes. We should maybe put removed deprecations in the breaking section and if we have new ones then maybe a new deprecation section.

[LeeTibbert]

re: removed & new deprecation items. Sounds good to me.

Do you want to drop in those headers where you think they should go so that they
are in a reasonable place when the first person comes along with deprecation items?
I am not trying to slough off work. Unity of design, especially at the beginning, comes
through to the reader. I am suggesting a "low stress" edit, they can always be
moved or rearranged.

A thought.

[LeeTibbert]

It is not said often enough or by enough people, but thank you for your housekeeping and supervision
work, such as this.

[WojciechMazur]

I've created a repo with to-be-removed methods, can to you take a look does it contain all removed interfaces? Also, I've seen that probably some of the URI or URL-related classes might be not removed, was that expected?
https://github.com/scala-native/scala-native-java-stubs is currently a private repo with limited access until the release 0.5.0. I didn't want to leave it public, as it might be confusing until its first release.

[ekrich]

URLEncoder and URLDecoder are not just stubs and one of them is also in Scala.js. The others I removed are only stubs - they were added just to make sconfig work. Since then we have recommended adding stubs to the projects that need them if the implementations are not going to be added to Scala Native.

I think the original intent was to have a place for the security code but that is more tangled than expected so far.

[ekrich]

@WojciechMazur This is ready for review. Might go first as it adds the 0.5.0 release notes that we can add to in subsequent PRs.