TST: add test for duplicated frame/test_analytics

[h-vetinari]

Preparation for #21645

Added some parametrised tests for duplicated.

In addition, I reordered the tests slightly. Currently, the tests in tests/frame/test_analytics.py test the following functions in order:

drop_duplicates
duplicated
duplicated
drop_duplicates
drop_duplicates
[...]

Since I am (and will be) adding several tests for duplicated, I'd like to group them within the code, and moved the two existing tests for duplicated to the top of that section.

[h-vetinari]

One single test failure in 1/7 jobs is unrelated:

E           AssertionError: Caused unexpected warning(s): [('ResourceWarning',
ResourceWarning("unclosed file <_io.BufferedReader name='/var/folders/bb/n7t3rs157850byt_jfdcq9k80000gn/T/tmptvrq0c3stest_file.zip'>",),
'/Users/travis/miniconda3/envs/pandas/lib/python3.5/site-packages/pluggy/__init__.py', 139)].

[jreback]

can you move the duplicated test into a new file frame/test_duplicates. same for series (you can move unique too as well)

[codecov]

Codecov Report

Merging #21898 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #21898      +/-   ##
==========================================
+ Coverage   91.91%   91.96%   +0.05%     
==========================================
  Files         164      166       +2     
  Lines       49992    50323     +331     
==========================================
+ Hits        45951    46281     +330     
- Misses       4041     4042       +1

Flag	Coverage Δ
#multiple	90.36% <ø> (+0.06%)	⬆️
#single	42.23% <ø> (+0.07%)	⬆️

Impacted Files	Coverage Δ
pandas/core/indexes/timedeltas.py	91.53% <0%> (-0.65%)	⬇️
pandas/core/indexes/base.py	96.35% <0%> (-0.23%)	⬇️
pandas/core/indexes/datetimes.py	95.16% <0%> (-0.18%)	⬇️
pandas/core/algorithms.py	94.69% <0%> (-0.16%)	⬇️
pandas/io/packers.py	88.04% <0%> (-0.16%)	⬇️
pandas/core/dtypes/common.py	95.07% <0%> (ø)	⬆️
pandas/core/arrays/__init__.py	100% <0%> (ø)	⬆️
pandas/core/dtypes/inference.py	98.41% <0%> (ø)	⬆️
pandas/core/arrays/timedelta.py
pandas/core/arrays/timedeltas.py	89.84% <0%> (ø)
... and 14 more

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[jreback]

thanks

[jreback]

thanks @h-vetinari