BUG: Return local Timestamp.weekday_name attribute (#17354)
- [x] closes #17354
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

@jreback created a new method `_get_named_field` based on your [comment](https://github.com/pandas-dev/pandas/issues/17354#issuecomment-325319229) in the issue thread.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=h1) Report
> Merging [#17377](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8351f86a0079b6b0cb95414807a2c2248530ef2c?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17377/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17377      +/-   ##
==========================================
- Coverage   91.16%   91.14%   -0.02%     
==========================================
  Files         163      163              
  Lines       49581    49581              
==========================================
- Hits        45199    45190       -9     
- Misses       4382     4391       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.92% <ø> (ø)` | :arrow_up: |
| #single | `40.25% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.72% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=footer). Last update [8351f86...18852f4](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=h1) Report
> Merging [#17377](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8351f86a0079b6b0cb95414807a2c2248530ef2c?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17377/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17377      +/-   ##
==========================================
- Coverage   91.16%   91.14%   -0.03%     
==========================================
  Files         163      163              
  Lines       49581    49587       +6     
==========================================
- Hits        45199    45194       -5     
- Misses       4382     4393      +11
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.92% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.25% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/io/parquet.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnF1ZXQucHk=) | `65.38% <0%> (-0.37%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.72% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.29% <0%> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.9% <0%> (ø)` | :arrow_up: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `82.69% <0%> (+0.01%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=footer). Last update [8351f86...ddaa4e3](https://codecov.io/gh/pandas-dev/pandas/pull/17377?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 cdef'd `_maybe_convert_value_to_local` and `val` argument in related function and all green.  thanks!