Simplify the construction of `x / 1` and `x / -1`

[github-actions[bot]]

Benchmark Results

	master	d2521fe36033fc...	master/d2521fe36033fc...
overhead/acrule/a+2	0.744 ± 0.016 μs	0.736 ± 0.015 μs	1.01
overhead/acrule/a+2+b	0.736 ± 0.015 μs	0.732 ± 0.016 μs	1.01
overhead/acrule/a+b	0.259 ± 0.0072 μs	0.265 ± 0.015 μs	0.978
overhead/acrule/noop:Int	25.3 ± 0.051 ns	25 ± 0.05 ns	1.01
overhead/acrule/noop:Sym	0.0342 ± 0.0049 μs	0.0387 ± 0.0057 μs	0.884
overhead/rule/noop:Int	0.0379 ± 0.00047 μs	0.0368 ± 0.00083 μs	1.03
overhead/rule/noop:Sym	0.0414 ± 0.0018 μs	0.042 ± 0.0014 μs	0.988
overhead/rule/noop:Term	0.0416 ± 0.0015 μs	0.0424 ± 0.0014 μs	0.98
overhead/ruleset/noop:Int	0.121 ± 0.0022 μs	0.12 ± 0.0016 μs	1.01
overhead/ruleset/noop:Sym	0.134 ± 0.0049 μs	0.137 ± 0.003 μs	0.98
overhead/ruleset/noop:Term	3.46 ± 0.22 μs	3.35 ± 0.15 μs	1.03
overhead/simplify/noop:Int	0.156 ± 0.00084 μs	0.151 ± 0.0012 μs	1.04
overhead/simplify/noop:Sym	0.174 ± 0.0021 μs	0.152 ± 0.0021 μs	1.15
overhead/simplify/noop:Term	0.038 ± 0.0019 ms	0.0388 ± 0.0029 ms	0.98
overhead/simplify/randterm (+, *):serial	0.118 ± 0.0012 s	0.118 ± 0.0027 s	0.998
overhead/simplify/randterm (+, *):thread	0.074 ± 0.023 s	0.0743 ± 0.025 s	0.995
overhead/simplify/randterm (/, *):serial	0.221 ± 0.0068 ms	0.229 ± 0.0074 ms	0.965
overhead/simplify/randterm (/, *):thread	0.248 ± 0.0078 ms	0.259 ± 0.0084 ms	0.956
overhead/substitute/a	0.0609 ± 0.0015 ms	0.0589 ± 0.0015 ms	1.03
overhead/substitute/a,b	0.0532 ± 0.0016 ms	0.0516 ± 0.0014 ms	1.03
overhead/substitute/a,b,c	16.6 ± 0.68 μs	16.7 ± 0.89 μs	0.996
polyform/easy_iszero	0.033 ± 0.0019 ms	0.032 ± 0.0018 ms	1.03
polyform/isone	2.79 ± 0.01 ns	3.1 ± 0.01 ns	0.9
polyform/iszero	1.79 ± 0.037 ms	1.75 ± 0.038 ms	1.02
polyform/simplify_fractions	2.39 ± 0.046 ms	2.34 ± 0.045 ms	1.02
time_to_load	4.57 ± 0.021 s	4.56 ± 0.015 s	1

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).

[YingboMa]

The test failure is unrelated.