CLN: ASV FromDictwithTimestamp
- [x] closes #18511

Also removed unnecessary `self`s and simplified method names

```
$ asv run -q -b ^frame_ctor
[  0.00%] ·· Benchmarking conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[ 16.67%] ··· Running frame_ctor.FromDicts.time_dict                                              6.66ms
[ 33.33%] ··· Running frame_ctor.FromDicts.time_list_of_dict                                       114ms
[ 50.00%] ··· Running frame_ctor.FromDicts.time_nested_dict                                       94.1ms
[ 66.67%] ··· Running frame_ctor.FromDicts.time_nested_dict_int64                                  240ms
[ 83.33%] ··· Running frame_ctor.FromDictwithTimestamp.time_dict_with_timestamp_offsets       76.5ms;...
[100.00%] ··· Running frame_ctor.FromSeries.time_mi_series                                         328μs
```
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18527?src=pr&el=h1) Report
> Merging [#18527](https://codecov.io/gh/pandas-dev/pandas/pull/18527?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1eedcf664cab1ca23a1d10071b2b7fb8095d0160?src=pr&el=desc) will **increase** coverage by `0.13%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18527/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18527?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18527      +/-   ##
==========================================
+ Coverage   91.44%   91.58%   +0.13%     
==========================================
  Files         157      153       -4     
  Lines       51378    51273     -105     
==========================================
- Hits        46985    46960      -25     
+ Misses       4393     4313      -80
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.45% <ø> (+0.15%)` | :arrow_up: |
| #single | `40.68% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18527?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/util/\_test\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3RfZGVjb3JhdG9ycy5weQ==) | `93.33% <0%> (-1.91%)` | :arrow_down: |
| [pandas/stats/moments.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL3N0YXRzL21vbWVudHMucHk=) | `70.81% <0%> (-0.39%)` | :arrow_down: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.28% <0%> (-0.16%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.59% <0%> (-0.13%)` | :arrow_down: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `82.37% <0%> (-0.13%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.81% <0%> (-0.1%)` | :arrow_down: |
| [pandas/tseries/frequencies.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvZnJlcXVlbmNpZXMucHk=) | `94.02% <0%> (-0.08%)` | :arrow_down: |
| [pandas/io/json/normalize.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vbm9ybWFsaXplLnB5) | `96.87% <0%> (-0.07%)` | :arrow_down: |
| [pandas/core/window.py](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvd2luZG93LnB5) | `96.31% <0%> (-0.07%)` | :arrow_down: |
| ... and [31 more](https://codecov.io/gh/pandas-dev/pandas/pull/18527/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18527?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/18527?src=pr&el=footer). Last update [1eedcf6...4de542f](https://codecov.io/gh/pandas-dev/pandas/pull/18527?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 cc @jbrockmendel we cover offsets already I believe, so this is superflous. @jorisvandenbossche Much appreciated if you could have a look.  @mroeschke Thanks!