Adding Preferences.jl as Dep

[cmhamel]

Adding Preferences.jl as dep to allow for setting up machine/architecture specific settings without having to touch source code.

Now consumer packages (e.g. Carina.jl) can provide a toml file LocalPreferences.toml to override the default kernel block size of 256 for all the assembly methods currently in the package except for the WIP block assemblers for mixed fem spaces.

An example file that overrides the matrix free action and vector kernel block sizes would look like

[FiniteElementContainers]
assemble_matrix_free_action_gpu_block_size = 64
assemble_vector_gpu_block_size = 512

This can be used to set optimal system settings for different machines.

[codecov]

Codecov Report

❌ Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 68.48%. Comparing base (ad91ed8) to head (9253fa3).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/assemblers/WeaklyEnforcedBCs.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
- Coverage   68.99%   68.48%   -0.51%     
==========================================
  Files          55       55              
  Lines        6525     6591      +66     
==========================================
+ Hits         4502     4514      +12     
- Misses       2023     2077      +54     

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