DEPR: Deprecate from_csv in favor of read_csv
Title is self-explanatory.  Closes #4191.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=h1) Report
> Merging [#17812](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3ba2cffff4c851460d3a2dbe893955dc9d9d0640?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17812/graphs/tree.svg?height=150&token=eZ4WkYLtcO&src=pr&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17812      +/-   ##
==========================================
- Coverage   91.24%   91.22%   -0.02%     
==========================================
  Files         163      163              
  Lines       49994    49995       +1     
==========================================
- Hits        45615    45607       -8     
- Misses       4379     4388       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.02% <100%> (ø)` | :arrow_up: |
| #single | `40.24% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.89% <ø> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.74% <100%> (-0.1%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17812?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/17812?src=pr&el=footer). Last update [3ba2cff...28f8097](https://codecov.io/gh/pandas-dev/pandas/pull/17812?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback : I took out all but a few instances of `from_csv` for testing purposes, and all is green.  PTAL. need a whatsnew note > need a whatsnew note

Oops.  Added. @jreback : Added `whatsnew`.  PTAL. pls add ``from_csv`` to the class level ``_deprecations`` parameter > pls add from_csv to the class level _deprecations parameter

Yep, done as well. lgtm. merge on green.