move implementation of Timedelta to tslibs.timedeltas (#18085)

Author: jbrockmendel

Diff for: pandas/_libs/period.pyx

@@ -30,6 +30,7 @@ from pandas._libs import tslib
 from pandas._libs.tslib import Timestamp, iNaT, NaT
 from tslibs.timezones cimport (
     is_utc, is_tzlocal, get_utcoffset, get_dst_info, maybe_get_tz)
+from tslibs.timedeltas cimport delta_to_nanoseconds
 
 from tslibs.parsing import parse_time_string, NAT_SENTINEL
 from tslibs.frequencies cimport get_freq_code
@@ -716,8 +717,8 @@ cdef class _Period(object):
         if isinstance(other, (timedelta, np.timedelta64, offsets.Tick)):
             offset = frequencies.to_offset(self.freq.rule_code)
             if isinstance(offset, offsets.Tick):
-                nanos = tslib._delta_to_nanoseconds(other)
-                offset_nanos = tslib._delta_to_nanoseconds(offset)
+                nanos = delta_to_nanoseconds(other)
+                offset_nanos = delta_to_nanoseconds(offset)
 
                 if nanos % offset_nanos == 0:
                     ordinal = self.ordinal + (nanos // offset_nanos)

Diff for: pandas/_libs/src/inference.pyx

@@ -3,7 +3,8 @@ from decimal import Decimal
 cimport util
 cimport cython
 from tslibs.nattype import NaT
-from tslib cimport convert_to_tsobject, convert_to_timedelta64
+from tslib cimport convert_to_tsobject
+from tslibs.timedeltas cimport convert_to_timedelta64
 from tslibs.timezones cimport get_timezone
 from datetime import datetime, timedelta
 iNaT = util.get_nat()

Diff for: pandas/_libs/tslib.pxd

@@ -2,7 +2,6 @@ from numpy cimport ndarray, int64_t
 
 from tslibs.conversion cimport convert_to_tsobject
 
-cpdef convert_to_timedelta64(object, object)
 cdef bint _check_all_nulls(obj)
 
 cdef _to_i8(object val)