fix: add literal_pow for composable expression

[MilesCranmer]

No description provided.

[github-actions]

Benchmark Results

	master	f49ea9d...	master/f49ea9d391938a...
search/multithreading	16.8 ± 1.6 s	16.4 ± 1.7 s	1.02
search/serial	28.5 ± 0.36 s	28.3 ± 0.099 s	1.01
utils/best_of_sample	1.65 ± 1.5 μs	1.75 ± 1.6 μs	0.942
utils/check_constraints_x10	11.2 ± 2.8 μs	11.1 ± 2.8 μs	1.01
utils/compute_complexity_x10/Float64	2.1 ± 0.11 μs	2.09 ± 0.1 μs	1
utils/compute_complexity_x10/Int64	2.06 ± 0.11 μs	2.04 ± 0.11 μs	1.01
utils/compute_complexity_x10/nothing	1.44 ± 0.13 μs	1.44 ± 0.11 μs	1
utils/insert_random_op_x10	5.83 ± 1.9 μs	5.86 ± 1.8 μs	0.995
utils/next_generation_x100	0.426 ± 0.091 ms	0.426 ± 0.065 ms	0.999
utils/optimize_constants_x10	0.0343 ± 0.0081 s	0.0341 ± 0.0072 s	1.01
utils/randomly_rotate_tree_x10	5.23 ± 0.57 μs	5.22 ± 0.59 μs	1
time_to_load	1.88 ± 0.012 s	1.87 ± 0.0063 s	1.01

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).

[coveralls]

Pull Request Test Coverage Report for Build 12508951273

Details

• 6 of 7 (85.71%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on literal-pow at 94.732%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ComposableExpression.jl	6	7	85.71%

Totals
Change from base Build 12508942839:	94.7%
Covered Lines:	3147
Relevant Lines:	3322

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💛 - Coveralls