* Merge RubyGems-3.5.12 and Bundler-2.5.12

* Merge RubyGems-3.5.13 and Bundler-2.5.13

* Merge RubyGems-3.5.14 and Bundler-2.5.14

* Merge RubyGems-3.5.15 and Bundler-2.5.15

* Merge RubyGems-3.5.16 and Bundler-2.5.16

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

https://github.com/rubygems/rubygems/commit/966daf7d42

For Ruby re-distributors, automatic user-install might be the right
default. Therefore printing warning about installing into user directory
is not always desirable. Let the default_user_install method be
customizable.

https://github.com/rubygems/rubygems/commit/2320dba544

This was issue previously, so hopefully this comment tries to state this
explicitly for future readers.

https://github.com/rubygems/rubygems/commit/8ccd830f85

The `options[:user_install]` might have three states:
* `true`: `--user-install`
* `false`: `--no-user-install` and
* `nil`: option was not specified

However, this had not been respected previously and the `false` and `nil`
were treated the same. This could lead to auto user installation despite
`--no-user-install` being specified on the command line.

Fixes https://github.com/rubygems/rubygems/pull/7237

https://github.com/rubygems/rubygems/commit/9281545474

https://github.com/rubygems/rubygems/commit/4b4d9c0106

For now, on a small rails app I have hanging around:

```
==> memprof.after.txt <==
Total allocated: 872.51 MB (465330 objects)
Total retained:  40.48 kB (326 objects)

==> memprof.before.txt <==
Total allocated: 890.79 MB (1494026 objects)
Total retained:  40.40 kB (328 objects)
```

Not a huge difference in memory usage, but it's a drastic improvement
in total number of allocations.

Additionally, this will pay huge dividends once
https://github.com/ruby/zlib/pull/61 is merged, as it will allow us to
completely avoid allocations in the repeated calls to readpartial,
which currently accounts for most of the memory usage shown above.

https://github.com/rubygems/rubygems/commit/f78d45d927