Change BlockArrays.jl from dep to weakdep

[mtfishman]

Builds on top of #120.

To-do:

• Fix and re-enable skipped blockedtuple tests (not all are re-enabled but important functionality is implemented and regressions are marked as broken).

[codecov]

Codecov Report

❌ Patch coverage is 92.98246% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.56%. Comparing base (fea87c5) to head (6b6442d).
⚠️ Report is 2 commits behind head on mf/biperm-interface.

Files with missing lines	Patch %	Lines
ext/TensorAlgebraBlockArraysExt/blockedtuple.jl	86.66%	2 Missing ⚠️
src/blockedtuple.jl	93.10%	2 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                   @@
##           mf/biperm-interface     #121      +/-   ##
=======================================================
+ Coverage                71.99%   72.56%   +0.57%     
=======================================================
  Files                       22       24       +2     
  Lines                     1114     1152      +38     
=======================================================
+ Hits                       802      836      +34     
- Misses                     312      316       +4     

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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