[C++][Dataset] Allow creating FileSystemDataset with FileInfoGenerator as a source

**Reporter**: [Pavel Solodovnikov](https://issues.apache.org/jira/browse/ARROW-17396) / @ManManson

_{**Note**: *This issue was originally created as [ARROW-17396](https://issues.apache.org/jira/browse/ARROW-17396). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the C++ implementations and tests for FileSystemDataset creation, then trace how FileInfoGenerator is currently represented as a source. The issue is complete when a FileInfoGenerator can be accepted for creating a FileSystemDataset and the relevant behavior is covered by tests; the issue provides no file or test paths.

Written by the indexing model from the issue text.