This pattern is extremely common across the ecosystem, I don't think
it's reasonable to deprecate it.

I understand the performance argument, but perhaps the dependency
resolution algorithm can use another method that is private API
and only works with two `Version` instance.

https://github.com/ruby/rubygems/commit/024b4b547a

https://github.com/ruby/rubygems/commit/fbf6fb667e

Comparing version objects is a huge bottleneck in dependency solvers
(like inside Bundler).  I would like to make comparing version objects
cheaper.  Right now we support comparing version objects with strings by
trying to coerce the string to a version.  So for example:

```ruby
Gem::Version.new("1") <=> "12"
```

I would like to deprecate and remove support for this feature so that we
can reduce the overhead of `def <=>`.

I'm not sure what version of RubyGems we could remove this from though.

https://github.com/ruby/rubygems/commit/81b7602183

It seems like we were trying to deprecate passing `nil` to
Gem::Version.new.  This breaks existing code, and I don't think there is
a good reason to deprecate this usage.

I believe what we want to prevent is the following code:

```ruby
Gem::Specification.new do |spec|
  spec.version = nil
  # suddenly the spec version is 0!
  p spec.version
end
```

This commit allows people to manually construct `Gem::Version.new(nil)`,
but when someone assigns `nil` as the Gem specification version, it sets
the spec version to `nil` (making the specification invalid).  People
who manually construct `Gem::Version` objects and use nil should be
allowed to do it, and `Gem::Version.new(nil) == Gem::Version.new("0")`,
but people who assign `nil` in a gemspec will get an invalid gemspec.

I think deprecation started
[here](https://github.com/ruby/rubygems/pull/2203) but there doesn't
seem to be a reason to do it.

Fixes https://github.com/ruby/rubygems/pull/9052

https://github.com/ruby/rubygems/commit/ded5e909c2

https://github.com/rubygems/rubygems/commit/5c88c77873

  from https://github.com/rubygems/rubygems/commit/0635c1423db5d7c461d53bf0c3329bca75de7609

https://github.com/rubygems/rubygems/commit/a4ba1a4d97