REF/INT: refactor concatenation of values in Block.concat_same_type

[jorisvandenbossche]

See comment #17954 (comment) and #17728 (comment) about suggestions to make the implementation of concat_same_type cleaner.

[jbrockmendel]

Block.concat_same_type is gone, is this closeable/updateable?

[jorisvandenbossche]

Yes, this can indeed be closed I think. The referenced comments are now also outdated with the introduction of the get_common_dtype interface used in the concat code.