Fix creation of database indexes (GH8083)

Tests fix

Fixes

Remove _executefunc

Fixed tests to work with Python3

Fix merge

Index test simplify

Test fix
Merge pull request #8083 from artemyk/to_sql_create_indexes

BUG: When creating table, db indexes should be created from DataFrame indexes
ENH: TimedeltaIndex and Timedelta scalar support (GH3009)

BUG: coercion of timedeltas in assignment (GH8209)

TST: skip sql.timedelta tests for now

COMPAT: provide conversion for passing in non-ns datetime64/timedelta64

BUG: diff on Dataframe with timedelta64 broken (GH4533)
DOC: move timedeltas to new section
ENH: support for alternate Timedelta format constructors in natural language (GH8190)
fixup astyping / freq conversion