remove deepcopy from grad! and obj!

[grishabh147]

This PR brings the following two changes:

• Removes unnecessary code from the test directory
• updates grad! and obj! implementations for augmented nlp blocks.

[codecov-commenter]

Codecov Report

Merging #9 (8971776) into main (5c3e038) will decrease coverage by 0.41%. The diff coverage is 85.71%.

@@            Coverage Diff             @@
##             main       #9      +/-   ##
==========================================
- Coverage   83.42%   83.00%   -0.42%     
==========================================
  Files           6        6              
  Lines         362      359       -3     
==========================================
- Hits          302      298       -4     
- Misses         60       61       +1     

Impacted Files	Coverage Δ
src/prox_augmented_block.jl	70.49% <75.00%> (-2.09%)	:arrow_down:
src/augmented_block.jl	82.05% <100.00%> (-0.88%)	:arrow_down:

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