Use structural equality in symbol expression optimizations

[neuralsorcerer]

Changes:

• Introduced a CanonicalValue enum and numeric canonicalization routine so integers, reals, and complex values are normalized before encoding.
• Implemented canonical fingerprint generation for SymbolExpr, which flattens sums and products, sorts normalized terms, and encodes nodes, symbols, and operators into deterministic byte sequences.

Why?

• Closes String-based comparisons in symbolic expression operations #14819

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Thank you for opening a new pull request.

Before your PR can be merged it will first need to pass continuous integration tests and be reviewed. Sometimes the review process can be slow, so please be patient.

While you're waiting, please feel free to review other open PRs. While only a subset of people are authorized to approve pull requests for merging, everyone is encouraged to review open pull requests. Doing reviews helps reduce the burden on the core team and helps make the project's code better for everyone.

One or more of the following people are relevant to this code:

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[coveralls]

Pull Request Test Coverage Report for Build 18256607998

Details

• 309 of 335 (92.24%) changed or added relevant lines in 1 file are covered.
• 22 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.03%) to 88.251%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/circuit/src/parameter/symbol_expr.rs	309	335	92.24%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	2	92.03%
crates/qasm2/src/parse.rs	6	97.56%
crates/circuit/src/parameter/symbol_expr.rs	14	75.29%

Totals
Change from base Build 18229727033:	0.03%
Covered Lines:	93421
Relevant Lines:	105858

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💛 - Coveralls