GH1063 Remove deprecated methods

[loicdiridollou]

• Closes Migration to 2.0 - Deprecation in Resample #1063
• Tests added: Please use assert_type() to assert the type of any return value

Series/DataFrame pad/backfill did not exist in the stubs.
Int64Index, UInt64Index and Float64Index did not exist in the stubs.
pandas.io.sql.execute did not exist in the stubs.

• Deprecated unused arguments *args and **kwargs in Resampler
• Deprecated Series.pad()
• Deprecated Series.backfill()
• Deprecated DataFrame.pad()
• Deprecated DataFrame.backfill()
• Deprecated close(). Use StataReader as a context manager instead
• Removed Int64Index, UInt64Index and Float64Index.''
• Deprecated argument infer_datetime_format in to_datetime() and read_csv(), as a strict version of it is now the default
• Deprecated pandas.io.sql.execute()

[Dr-Irv]

Thanks @loicdiridollou