feat!: create ReadOnlyNode for StructuredExpression get_tree access

[MilesCranmer]

No description provided.

[github-actions]

Benchmark Results

	master	04f9816...	master/04f98161de8423...
eval/ComplexF32/evaluation	7.29 ± 0.55 ms	7.26 ± 0.52 ms	1
eval/ComplexF64/evaluation	10.7 ± 0.93 ms	10.8 ± 0.89 ms	0.997
eval/Float32/derivative	11.9 ± 1.4 ms	11.6 ± 1.1 ms	1.02
eval/Float32/derivative_turbo	11.7 ± 1.2 ms	11.8 ± 1.3 ms	0.991
eval/Float32/evaluation	2.75 ± 0.26 ms	2.74 ± 0.25 ms	1
eval/Float32/evaluation_bumper	0.608 ± 0.015 ms	0.607 ± 0.013 ms	1
eval/Float32/evaluation_turbo	0.586 ± 0.033 ms	0.581 ± 0.029 ms	1.01
eval/Float32/evaluation_turbo_bumper	0.608 ± 0.014 ms	0.606 ± 0.013 ms	1
eval/Float64/derivative	15.7 ± 0.76 ms	15.5 ± 0.83 ms	1.02
eval/Float64/derivative_turbo	15.8 ± 0.72 ms	15.3 ± 0.86 ms	1.03
eval/Float64/evaluation	3.21 ± 0.28 ms	3.2 ± 0.31 ms	1
eval/Float64/evaluation_bumper	1.26 ± 0.042 ms	1.26 ± 0.045 ms	1.01
eval/Float64/evaluation_turbo	1.06 ± 0.064 ms	1.07 ± 0.065 ms	0.996
eval/Float64/evaluation_turbo_bumper	1.27 ± 0.039 ms	1.26 ± 0.04 ms	1.01
utils/combine_operators/break_sharing	0.0381 ± 0.00052 ms	0.0387 ± 0.00074 ms	0.985
utils/convert/break_sharing	27.6 ± 2.3 μs	27.5 ± 2.4 μs	1.01
utils/convert/preserve_sharing	0.0979 ± 0.0037 ms	0.0992 ± 0.0042 ms	0.987
utils/copy/break_sharing	28.5 ± 2.4 μs	28.5 ± 2.2 μs	1
utils/copy/preserve_sharing	0.0982 ± 0.0041 ms	0.0997 ± 0.0039 ms	0.985
utils/count_constant_nodes/break_sharing	8.81 ± 0.22 μs	8.98 ± 0.17 μs	0.982
utils/count_constant_nodes/preserve_sharing	0.0865 ± 0.0033 ms	0.0858 ± 0.0032 ms	1.01
utils/count_depth/break_sharing	9.76 ± 0.25 μs	9.59 ± 0.21 μs	1.02
utils/count_nodes/break_sharing	8.98 ± 0.2 μs	8.24 ± 0.19 μs	1.09
utils/count_nodes/preserve_sharing	0.0861 ± 0.0036 ms	0.0864 ± 0.0033 ms	0.997
utils/get_set_constants!/break_sharing	0.033 ± 0.002 ms	0.0342 ± 0.0021 ms	0.962
utils/get_set_constants!/preserve_sharing	0.177 ± 0.0057 ms	0.176 ± 0.0054 ms	1.01
utils/get_set_constants_parametric	0.0447 ± 0.0023 ms	0.046 ± 0.0025 ms	0.971
utils/has_constants/break_sharing	4.09 ± 0.14 μs	4.13 ± 0.16 μs	0.99
utils/has_operators/break_sharing	2.21 ± 0.066 μs	2.02 ± 0.078 μs	1.09
utils/hash/break_sharing	23.1 ± 0.66 μs	22.8 ± 0.59 μs	1.01
utils/hash/preserve_sharing	0.0975 ± 0.0034 ms	0.0972 ± 0.0035 ms	1
utils/index_constant_nodes/break_sharing	25.5 ± 1.1 μs	25.2 ± 1.5 μs	1.01
utils/index_constant_nodes/preserve_sharing	0.1 ± 0.0037 ms	0.0979 ± 0.0033 ms	1.02
utils/is_constant/break_sharing	4.68 ± 0.19 μs	4.44 ± 0.2 μs	1.06
utils/simplify_tree/break_sharing	0.174 ± 0.0031 ms	0.181 ± 0.0034 ms	0.962
utils/simplify_tree/preserve_sharing	0.226 ± 0.0055 ms	0.234 ± 0.0043 ms	0.966
utils/string_tree/break_sharing	0.48 ± 0.014 ms	0.482 ± 0.015 ms	0.995
utils/string_tree/preserve_sharing	0.59 ± 0.017 ms	0.595 ± 0.021 ms	0.993
time_to_load	0.217 ± 0.007 s	0.214 ± 0.0052 s	1.01

[github-actions]

Pull Request Test Coverage Report for Build 11318576297

Details

• 13 of 14 (92.86%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 95.345%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ReadOnlyNode.jl	10	11	90.91%

Totals
Change from base Build 11317287088:	-0.02%
Covered Lines:	2417
Relevant Lines:	2535

---

💛 - Coveralls