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
BUG: boxplot fails when one column is all NaNs

Add test case for empty column

Replace empty arrays with [np.nan]

Add fix to the release notes

Add issue numbers