CI: Add 'conda list' for azure/posix after activate 'pandas-dev'
Running into debugging problems in #24984 because `conda list` is never called after installing the `pandas-dev` environment.

It seems that this is just missing in azure/posix (I reflected the comment in other locations not least to show where else this is already done).
I thought this should show up when you run `conda install` ?  Or do we not do that here? @gfyoung 
Check out an azure posix build, e.g. [this line and below](https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=8549&view=logs&jobId=bc6b51b3-ab2f-50b8-43d9-45e2b4669322&taskId=f559f56a-b466-55ac-252e-11ab522c7a56&lineStart=406&lineEnd=406&colStart=6&colEnd=56), there's nothing after the env is installed.

It *is* present in the windows-equivalent, see the diff (where I add the comment) # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=h1) Report
> Merging [#25377](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b2c751985ebd09b72d917d08dc06193dc0922018?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25377/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25377      +/-   ##
==========================================
- Coverage   91.73%   91.73%   -0.01%     
==========================================
  Files         173      173              
  Lines       52838    52838              
==========================================
- Hits        48472    48470       -2     
- Misses       4366     4368       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <ø> (-0.01%)` | :arrow_down: |
| #single | `41.29% <ø> (-0.43%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/excel/\_xlrd.py](https://codecov.io/gh/pandas-dev/pandas/pull/25377/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2V4Y2VsL194bHJkLnB5) | `91.04% <0%> (-2.99%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25377?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/25377?src=pr&el=footer). Last update [b2c7519...a953fd6](https://codecov.io/gh/pandas-dev/pandas/pull/25377?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/25377?src=pr&el=h1) Report
> Merging [#25377](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b2c751985ebd09b72d917d08dc06193dc0922018?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25377/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25377      +/-   ##
==========================================
- Coverage   91.73%   91.73%   -0.01%     
==========================================
  Files         173      173              
  Lines       52838    52838              
==========================================
- Hits        48472    48470       -2     
- Misses       4366     4368       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <ø> (-0.01%)` | :arrow_down: |
| #single | `41.29% <ø> (-0.43%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/excel/\_xlrd.py](https://codecov.io/gh/pandas-dev/pandas/pull/25377/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2V4Y2VsL194bHJkLnB5) | `91.04% <0%> (-2.99%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25377?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/25377?src=pr&el=footer). Last update [b2c7519...a953fd6](https://codecov.io/gh/pandas-dev/pandas/pull/25377?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @h-vetinari - I have a pending PR #24632 . Can you have a look? The PR unifies env creation script. Closing in favour of #24632.