Dispatch Series comparison ops to DatetimeIndex and TimedeltaIndex
Another couple steps towards unifying the implementations.

We will be able to simplify _comp_method_SERIES a lot if/when the Categorical vs CategoricalIndex inconsistencies are sorted out #19513.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19524?src=pr&el=h1) Report
> Merging [#19524](https://codecov.io/gh/pandas-dev/pandas/pull/19524?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/11de13140f66b7f04ded53f7890738061512df3b?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `88.23%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19524/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19524?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19524      +/-   ##
==========================================
- Coverage    91.6%   91.58%   -0.03%     
==========================================
  Files         150      150              
  Lines       48867    48866       -1     
==========================================
- Hits        44767    44755      -12     
- Misses       4100     4111      +11
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.96% <88.23%> (-0.03%)` | :arrow_down: |
| #single | `41.75% <64.7%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19524?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/19524/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `96.14% <88.23%> (-0.69%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/19524/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.22% <0%> (-1.74%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/19524/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.93% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/19524/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.41% <0%> (+0.09%)` | :arrow_up: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/19524/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.68% <0%> (+0.22%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19524?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/19524?src=pr&el=footer). Last update [11de131...a0c14cd](https://codecov.io/gh/pandas-dev/pandas/pull/19524?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 I can't seem to replicate the test failure.  Can anyone else?

```
ser = pd.Series([pd.Timestamp('2000-01-29 01:59:00'), 'NaT'])
result = ser != ser
assert (result == [False, True]).all()
``` I'm having no luck with replicating the error.  Closing for now, will revisit when the queue dies down. Most recent push was intended for my circleCI account, forgot it would get pushed here.  Will revert.  No luck SSHijg into circleCI so far.