Add phaser to functional

[bhargavkathivarapu]

Hi ,
Regarding the issue ( Reducing dependency in Sox - #260 )
Implemented phaser function in functional.py

• function.rst - updated with new function

• test_sox_compatibility.py - Added two tests for phaser

• test_batch_consistency.py - added test for phaser

• test_torchscript_consistency.py - added test for phaser

All CPU test passed.

@vincentqb could you please review these changes

[codecov]

Codecov Report

Merging #587 into master will increase coverage by 0.17%.
The diff coverage is 95.65%.

@@            Coverage Diff             @@
##           master     #587      +/-   ##
==========================================
+ Coverage   87.85%   88.03%   +0.17%     
==========================================
  Files          19       19              
  Lines        2051     2097      +46     
==========================================
+ Hits         1802     1846      +44     
- Misses        249      251       +2     

Impacted Files	Coverage Δ
torchaudio/functional.py	94.85% <95.65%> (+0.06%)	⬆️

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[vincentqb]

LGTM, thanks for working on this!

[mthrok]

FYI this fails on GPU. I will work on fix.

https://app.circleci.com/pipelines/github/pytorch/audio/1678/workflows/a734c025-4ab4-4a1d-b882-afbd3080231b/jobs/42638

[mthrok]

Fix -> #607