Deprecate implicit call API

[MilesCranmer]

Taking @Moelf's suggestion in #21, this PR deprecates (softly, using Base.depwarn) the functor syntax tree(X), which implicitly uses the last OperatorEnum() that was created.

This PR replaces it with the explicit functor syntax: tree(X, operators). Likewise for gradients: tree'(X, operators).

@Moelf do you think you could review?

Thanks! Miles

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fixes #21

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Pull Request Test Coverage Report for Build 4710033484

• 26 of 26 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 89.354%

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Totals
Change from base Build 4689134023:	0.1%
Covered Lines:	982
Relevant Lines:	1099

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💛 - Coveralls

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Benchmark Results

	master	601bd9350f4baa...	t[master]/t[601bd9350f4baa...]
OperatorEnum/ComplexF32/evaluation	0.0386 ± 0.0046 ms	0.0364 ± 0.0033 ms	1.06
OperatorEnum/ComplexF64/evaluation	0.0381 ± 0.0029 ms	0.0395 ± 0.0047 ms	0.965
OperatorEnum/Float32/derivative	0.138 ± 0.0021 ms	0.137 ± 0.002 ms	1.01
OperatorEnum/Float32/derivative_turbo	0.164 ± 0.012 ms	0.163 ± 0.014 ms	1
OperatorEnum/Float32/evaluation	8.18 ± 0.48 μs	8.05 ± 0.6 μs	1.02
OperatorEnum/Float32/evaluation_turbo	7.16 ± 0.62 μs	7.26 ± 0.83 μs	0.986
OperatorEnum/Float64/derivative	0.203 ± 0.0045 ms	0.2 ± 0.0046 ms	1.02
OperatorEnum/Float64/derivative_turbo	0.23 ± 0.017 ms	0.228 ± 0.014 ms	1.01
OperatorEnum/Float64/evaluation	12.4 ± 1.2 μs	12 ± 1.3 μs	1.03
OperatorEnum/Float64/evaluation_turbo	11.4 ± 1.2 μs	11.5 ± 1.4 μs	0.991

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).

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Benchmark Results

	master	715000d52c18b4...	t[master]/t[715000d52c18b4...]
OperatorEnum/ComplexF32/evaluation	0.0386 ± 0.0017 ms	0.0481 ± 0.016 ms	0.802
OperatorEnum/ComplexF64/evaluation	0.0369 ± 0.0031 ms	0.037 ± 0.002 ms	0.997
OperatorEnum/Float32/derivative	0.13 ± 0.0033 ms	0.128 ± 0.0038 ms	1.02
OperatorEnum/Float32/derivative_turbo	0.176 ± 0.0026 ms	0.175 ± 0.0022 ms	1.01
OperatorEnum/Float32/evaluation	8.27 ± 0.46 μs	8.3 ± 0.4 μs	0.997
OperatorEnum/Float32/evaluation_turbo	7.1 ± 0.48 μs	7.16 ± 0.38 μs	0.992
OperatorEnum/Float64/derivative	0.15 ± 0.0062 ms	0.151 ± 0.0035 ms	0.997
OperatorEnum/Float64/derivative_turbo	0.204 ± 0.0029 ms	0.204 ± 0.0041 ms	1
OperatorEnum/Float64/evaluation	12.1 ± 1.1 μs	12.1 ± 0.83 μs	1
OperatorEnum/Float64/evaluation_turbo	11.4 ± 1.4 μs	11.2 ± 1.2 μs	1.02

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).

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Benchmark Results

	master	8ff81588673290...	t[master]/t[8ff81588673290...]
OperatorEnum/ComplexF32/evaluation	0.0385 ± 0.0013 ms	0.0384 ± 0.0016 ms	1
OperatorEnum/ComplexF64/evaluation	0.0369 ± 0.003 ms	0.0365 ± 0.0015 ms	1.01
OperatorEnum/Float32/derivative	0.121 ± 0.0062 ms	0.128 ± 0.0033 ms	0.943
OperatorEnum/Float32/derivative_turbo	0.177 ± 0.0032 ms	0.176 ± 0.0021 ms	1.01
OperatorEnum/Float32/evaluation	7.62 ± 0.52 μs	7.58 ± 0.36 μs	1.01
OperatorEnum/Float32/evaluation_turbo	7.08 ± 0.48 μs	7 ± 0.38 μs	1.01
OperatorEnum/Float64/derivative	0.156 ± 0.005 ms	0.157 ± 0.0043 ms	0.999
OperatorEnum/Float64/derivative_turbo	0.204 ± 0.0044 ms	0.202 ± 0.0033 ms	1.01
OperatorEnum/Float64/evaluation	12.3 ± 1 μs	12 ± 0.9 μs	1.02
OperatorEnum/Float64/evaluation_turbo	11.4 ± 1 μs	11.1 ± 0.9 μs	1.03

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).

[Moelf]

sorry didn't have time to respond in time but this is great and thanks a lot for this!!