feat: use a global atomic UInt64 to give each BasicSymbolic a unique ID

[AayushSabharwal]

No description provided.

[github-actions]

Benchmark Results

	master	a4dabb3...	master/a4dabb33e02189...
overhead/acrule/a+2	0.969 ± 0.31 μs	1.01 ± 0.35 μs	0.96
overhead/acrule/a+2+b	0.96 ± 0.32 μs	1.23 ± 0.33 μs	0.782
overhead/acrule/a+b	0.263 ± 0.0062 μs	0.269 ± 0.026 μs	0.978
overhead/acrule/noop:Int	1.57 ± 0 ns	1.55 ± 0.01 ns	1.01
overhead/acrule/noop:Sym	27.8 ± 6 ns	27.1 ± 5.6 ns	1.02
overhead/rule/noop:Int	0.0359 ± 0.0021 μs	0.035 ± 0.026 μs	1.02
overhead/rule/noop:Sym	0.0327 ± 0.0088 μs	0.0337 ± 0.025 μs	0.97
overhead/rule/noop:Term	0.0329 ± 0.024 μs	0.0338 ± 0.025 μs	0.974
overhead/ruleset/noop:Int	0.117 ± 0.0041 μs	0.118 ± 0.003 μs	0.99
overhead/ruleset/noop:Sym	0.127 ± 0.01 μs	0.116 ± 0.0027 μs	1.09
overhead/ruleset/noop:Term	4.6 ± 0.84 μs	4.57 ± 0.1 μs	1.01
overhead/simplify/noop:Int	0.228 ± 0.027 μs	0.208 ± 0.0026 μs	1.1
overhead/simplify/noop:Sym	0.246 ± 0.032 μs	0.214 ± 0.0073 μs	1.15
overhead/simplify/noop:Term	0.0378 ± 0.0051 ms	0.05 ± 0.0017 ms	0.755
overhead/simplify/randterm (+, *):serial	0.0916 ± 0.0044 s	0.124 ± 0.0039 s	0.737
overhead/simplify/randterm (+, *):thread	0.0553 ± 0.0065 s	0.0721 ± 0.0067 s	0.766
overhead/simplify/randterm (/, *):serial	0.209 ± 0.027 ms	0.226 ± 0.019 ms	0.928
overhead/simplify/randterm (/, *):thread	0.241 ± 0.025 ms	0.262 ± 0.018 ms	0.918
overhead/substitute/a	0.0949 ± 0.012 ms	0.108 ± 0.012 ms	0.881
overhead/substitute/a,b	0.0871 ± 0.011 ms	0.0926 ± 0.01 ms	0.94
overhead/substitute/a,b,c	19.9 ± 2 μs	21.5 ± 2.6 μs	0.928
polyform/easy_iszero	0.04 ± 0.0065 ms	0.0408 ± 0.0011 ms	0.98
polyform/isone	3.11 ± 0.01 ns	3.1 ± 0.01 ns	1
polyform/iszero	1.33 ± 0.034 ms	1.39 ± 0.032 ms	0.956
polyform/simplify_fractions	1.82 ± 0.045 ms	1.9 ± 0.035 ms	0.956
time_to_load	1 ± 0.0085 s	1 ± 0.0051 s	0.998

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.
Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).

[AayushSabharwal]

This doesn't seem very worth for performance. I'll try and figure out how much it affects caching.