Improved `DenseLQDynamicModel` construction to require less memory and build faster

[dlcole3]

Reformulated source code to build the Hessian and Jacobian a block at a time for the dense model. Previously, all block matrices were built, stored, and then multiplied together, but this was very inefficient as many of the multiplications were redundant. Instead, each block within the block matrices were multiplied together only when needed within for loops.

This PR includes:

• redefining DenseLQDynamicBlocks to only save the A block and the B block. The latter block only contains the first column of the actual block B matrix, and it does not contain the first rows of zeros. This also removed any sparse matrices, which were inefficient within LinearAlgebra.mul!
• redefining _build_block_matrices to match DenseLQDynamicBlocks.
• redefining _build_H_blocks
• redefining _build_G_blocks.
• defining a new function, _build_dense_J1 to form the Jacobian from the G blocks
• updating build_dense_lq_dynamic_model to be consistent with these changes
• updating get_s and get_u for working with the new block B matrix

This PR does not include updating the sparse formulation (which is also somewhat inefficient) or redefining the internal functions to be non-allocating. These changes are still needed but will be met with other PRs.

[dlcole3]

I also updated the build_thinplate.jl file in the examples/ folder. This used the old DenseLQDynamicBlocks structure

[codecov-commenter]

Codecov Report

Merging #31 (b18f65b) into main (5aa725d) will increase coverage by 0.34%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #31      +/-   ##
==========================================
+ Coverage   97.44%   97.79%   +0.34%     
==========================================
  Files           1        1              
  Lines         705      724      +19     
==========================================
+ Hits          687      708      +21     
+ Misses         18       16       -2     

Impacted Files	Coverage Δ
src/DynamicNLPModels.jl	97.79% <100.00%> (+0.34%)	:arrow_up:

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[dlcole3]

@frapac I made one more change after requesting reviews again (sorry, I should've added it before requesting reviews). I realized I am allocating extra memory for the Jacobian. I essentially was buliding the Jacobian twice. I removed the extra J1, J2, and J3 matrices in the most recent commit.