Implement missing offset comparison methods
State: closed

- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Not sure if it closes #8386, but its most of the way there.

Fix some missing comparisons, including Timedelta with Tick and Tick with (timedelta|Timedelta|Week)

Attach correct names for comparison methods.

If we can resolve #18510, we can make `Week(weekday=None)` just return a `Tick`, avoid some special casing.

Labels:
name: API Design
name: Frequency
description: DateOffsets
name: Compat
description: pandas objects compatability with Numpy or Python functions

Comments:
> Not sure if it closes #8386, but its most of the way there.

if most of the way there, then let's take it over the line.

> if most of the way there, then let's take it over the line.

#8386 can be split into two parts.  First is unimplemented comparison methods, which this PR addresses as many of as I could find.

Second is that author implicitly expects `to_offset('W')` to return `pd.offsets.Week(weekday=None)` (which will after this PR be comparable as that author expects), but `to_offset('W')` actually returns `pd.offsets.Week(weekday=6)`, which remains non-comparable.  This latter part of that issue is not addressed in this PR, and I want to leave it up to @edrevo to decide if this fully solves the problem.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18738?src=pr&el=h1) Report
> Merging [#18738](https://codecov.io/gh/pandas-dev/pandas/pull/18738?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/75b97a70110b0d924a557bd8e7929bcf1f4509a2?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `82.05%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18738/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18738?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18738      +/-   ##
==========================================
- Coverage   91.67%   91.66%   -0.01%     
==========================================
  Files         154      154              
  Lines       51368    51388      +20     
==========================================
+ Hits        47092    47106      +14     
- Misses       4276     4282       +6
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.53% <82.05%> (-0.01%)` | :arrow_down: |
| #single | `40.83% <35.89%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18738?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/tseries/offsets.py](https://codecov.io/gh/pandas-dev/pandas/pull/18738/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvb2Zmc2V0cy5weQ==) | `96.53% <82.05%> (-0.42%)` | :arrow_down: |

------

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> **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/18738?src=pr&el=footer). Last update [75b97a7...c3f7a1f](https://codecov.io/gh/pandas-dev/pandas/pull/18738?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

@jbrockmendel , I'm OK with this fix. Many thanks for the PR!!
Handling array-like comparisons correctly is going to take some additional work.  Temporarily closing to clear the queue.