Refactor algorithm unit tests

[Red-Portal]

This refactor does the following:

• Restructures the existing unit tests to reflect the new project structure: One test file corresponding to each individual algorithm.
• Removes some redundant tests. (Reduce the CI time)
• Make the tests across algorithms more consistent.

[github-actions]

AdvancedVI.jl documentation for PR #213 is available at:
https://TuringLang.github.io/AdvancedVI.jl/previews/PR213/

[github-actions]

Benchmark Results

Benchmark suite	Current: 8fc81ad	Previous: 2574b48	Ratio
normal/RepGradELBO + STL/meanfield/Zygote	3975636232 ns	3799923741 ns	1.05
normal/RepGradELBO + STL/meanfield/ReverseDiff	1126251674 ns	1104804401 ns	1.02
normal/RepGradELBO + STL/meanfield/Mooncake	1232397137 ns	1210371921 ns	1.02
normal/RepGradELBO + STL/fullrank/Zygote	3954447715 ns	3827278384 ns	1.03
normal/RepGradELBO + STL/fullrank/ReverseDiff	1654004177.5 ns	1592215391.5 ns	1.04
normal/RepGradELBO + STL/fullrank/Mooncake	1260042397 ns	1244421336 ns	1.01
normal/RepGradELBO/meanfield/Zygote	2814991162 ns	2712235289 ns	1.04
normal/RepGradELBO/meanfield/ReverseDiff	791179867 ns	771193563 ns	1.03
normal/RepGradELBO/meanfield/Mooncake	1095518432 ns	1089065643 ns	1.01
normal/RepGradELBO/fullrank/Zygote	2816289444.5 ns	2749709318 ns	1.02
normal/RepGradELBO/fullrank/ReverseDiff	972813346.5 ns	934505754.5 ns	1.04
normal/RepGradELBO/fullrank/Mooncake	1127670033 ns	1126928504 ns	1.00
normal + bijector/RepGradELBO + STL/meanfield/Zygote	5562006335 ns	5367193378 ns	1.04
normal + bijector/RepGradELBO + STL/meanfield/ReverseDiff	2397825869 ns	2323372389 ns	1.03
normal + bijector/RepGradELBO + STL/meanfield/Mooncake	4126647817 ns	3960869500 ns	1.04
normal + bijector/RepGradELBO + STL/fullrank/Zygote	5569946276 ns	5434514027 ns	1.02
normal + bijector/RepGradELBO + STL/fullrank/ReverseDiff	3055640710.5 ns	2934181887.5 ns	1.04
normal + bijector/RepGradELBO + STL/fullrank/Mooncake	4240574498.5 ns	4057981600.5 ns	1.04
normal + bijector/RepGradELBO/meanfield/Zygote	4274462972.5 ns	4167634470.5 ns	1.03
normal + bijector/RepGradELBO/meanfield/ReverseDiff	2056947266 ns	1973359104 ns	1.04
normal + bijector/RepGradELBO/meanfield/Mooncake	3963762960 ns	3832884940 ns	1.03
normal + bijector/RepGradELBO/fullrank/Zygote	4378078308 ns	4306110983 ns	1.02
normal + bijector/RepGradELBO/fullrank/ReverseDiff	2326469538 ns	2235069606 ns	1.04
normal + bijector/RepGradELBO/fullrank/Mooncake	4117180369 ns	3912170803 ns	1.05

This comment was automatically generated by workflow using github-action-benchmark.