REF: Deduplicate array, infer_dtype, and maybe_convert_objects

[TomAugspurger]

There's some duplicate / slightly diverging functionality between pd.array, infer_dtype and convert_objects. Both pd.array and convert_objects are roughly "convert this list-like thing to this better array". See the conversation in #29799 (comment) for more.

Hopefully this can be deduplicated.

cc @jreback.

Followup to #29799

[jbrockmendel]

xref #27460