Apply hash consing to all BasicSymbolic subtypes

[Blablablanca]

• resolve Hash consing #614

• following Implement hash consing for Sym #658

(UROP under @bowenszhu)

[bowenszhu]

The last commit f2d7791 implements the change to hash2 to ensure that a [with metadata] + b and a [no metadata] + b have different hashes. The recursive approach now incorporates metadata and symtype information of nodes in symbolic tree, correctly distinguishing these cases. The hash2 function could be optimized further in a future PR, for example, by adding a field to the BasicSymbolic struct to cache hash values and avoid redundant computations. The ordering of symbolic objects is not dependent on hash2, allowing for future refactoring of this function.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 97.77778% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.04%. Comparing base (0288135) to head (d716d3b).
Report is 75 commits behind head on master.

Files with missing lines	Patch %	Lines
src/types.jl	97.77%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #673      +/-   ##
==========================================
+ Coverage   81.86%   82.04%   +0.18%     
==========================================
  Files          16       16              
  Lines        1908     1933      +25     
==========================================
+ Hits         1562     1586      +24     
- Misses        346      347       +1     

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