rb_feature_p: skip `get_expanded_load_path` for absolute paths
Ref: https://github.com/fxn/zeitwerk/pull/308
```ruby
require 'benchmark'
$LOAD_PATH << 'relative-path'
autoload :FOO, '/tmp/foo.rb'
puts Benchmark.realtime {
500_000.times do
Object.autoload?(:FOO)
end
}
```
The above script takes 2.5 seconds on `master`, and only
50ms on this branch.
When we're looking for a feature with an absolute path, we don't
need to call the expensive `get_expanded_load_path`.
Related issues
Bug #21032: `Module#autoload?` is slow when `$LOAD_PATH` contains a relative path
merge revision(s) d4a1a2780c39bc648496ac92fc6e6ce2eb38ab47: [Backport #21032]