cdef out dtype for _Timestamp._get_field

[mroeschke]

Follow-up to @jreback comment in #17377 to dtype the out variable in _get_field and get_named_field

Also, replaced value conversion in _get_start_end_field with _maybe_convert_value_to_local function created in #17377

[codecov]

Codecov Report

Merging #17457 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #17457      +/-   ##
==========================================
- Coverage   91.15%   91.14%   -0.02%     
==========================================
  Files         163      163              
  Lines       49591    49591              
==========================================
- Hits        45207    45198       -9     
- Misses       4384     4393       +9

Flag	Coverage Δ
#multiple	88.92% <ø> (ø)	⬆️
#single	40.25% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.72% <0%> (-0.1%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 20fee85...52a5f98. Read the comment docs.

[jreback]

thanks!