rb_feature_p: skip `get_expanded_load_path` for absolute paths

Ref: https://github.com/fxn/zeitwerk/pull/308

```ruby
require 'benchmark'

$LOAD_PATH << 'relative-path'

autoload :FOO, '/tmp/foo.rb'

puts Benchmark.realtime {
  500_000.times do
    Object.autoload?(:FOO)
  end
}
```

The above script takes 2.5 seconds on `master`, and only
50ms on this branch.

When we're looking for a feature with an absolute path, we don't
need to call the expensive `get_expanded_load_path`.

0 files changed, 0 insertions, 0 deletions