REF: dispatch Series.quantile to DataFrame, remove ScalarBlock

[jbrockmendel]

ScalarBlock exists because sometimes Block.quantile needs to return a scalar. By having Series dispatch to DataFrame, we simplify quantile in internals an get to remove ScalarBlock and make_block_scalar

[jreback]

lgtm. nice to get rid of this hack. do a git blame sometime and you will see who did this code :> (you have to go back before you moved it)

[codecov]

Codecov Report

Merging #24606 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24606      +/-   ##
==========================================
- Coverage   92.38%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52490    52474      -16     
==========================================
- Hits        48493    48473      -20     
- Misses       3997     4001       +4

Flag	Coverage Δ
#multiple	90.8% <100%> (-0.02%)	⬇️
#single	43.05% <9.09%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
pandas/core/internals/__init__.py	100% <ø> (ø)	⬆️
pandas/core/internals/managers.py	96.05% <100%> (+0.08%)	⬆️
pandas/core/internals/blocks.py	94.21% <100%> (-0.33%)	⬇️
pandas/core/series.py	93.56% <100%> (+0.02%)	⬆️
pandas/core/nanops.py	94.36% <0%> (-0.19%)	⬇️

---

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[codecov]

Codecov Report

Merging #24606 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24606      +/-   ##
==========================================
- Coverage   92.38%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52490    52474      -16     
==========================================
- Hits        48493    48473      -20     
- Misses       3997     4001       +4

Flag	Coverage Δ
#multiple	90.8% <100%> (-0.02%)	⬇️
#single	43.05% <9.09%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
pandas/core/internals/__init__.py	100% <ø> (ø)	⬆️
pandas/core/internals/managers.py	96.05% <100%> (+0.08%)	⬆️
pandas/core/internals/blocks.py	94.21% <100%> (-0.33%)	⬇️
pandas/core/series.py	93.56% <100%> (+0.02%)	⬆️
pandas/core/nanops.py	94.36% <0%> (-0.19%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9175387...a21dd35. Read the comment docs.

[jreback]

thanks!