Rename @template to @template_spec

[MilesCranmer]

I think @template is too generic so am renaming it.

[github-actions]

Benchmark Results

	master	8eeb51f...	master/8eeb51fe3583c4...
search/multithreading	17.4 ± 0.82 s	16.7 ± 0.24 s	1.04
search/serial	30.6 ± 0.49 s	30.2 ± 0.37 s	1.01
utils/best_of_sample	1.65 ± 0.47 μs	1.62 ± 0.72 μs	1.02
utils/check_constraints_x10	12.2 ± 3.4 μs	12.1 ± 3.3 μs	1.01
utils/compute_complexity_x10/Float64	2.16 ± 0.22 μs	2.15 ± 0.24 μs	1
utils/compute_complexity_x10/Int64	2.08 ± 0.67 μs	2.08 ± 0.22 μs	1
utils/compute_complexity_x10/nothing	1.47 ± 0.22 μs	1.46 ± 0.19 μs	1.01
utils/insert_random_op_x10	5.84 ± 2.1 μs	5.91 ± 2.2 μs	0.988
utils/next_generation_x100	0.363 ± 0.097 ms	0.364 ± 0.096 ms	0.997
utils/optimize_constants_x10	0.0375 ± 0.0087 s	0.0375 ± 0.0087 s	0.998
utils/randomly_rotate_tree_x10	5.5 ± 0.73 μs	5.47 ± 1.2 μs	1.01
time_to_load	2.04 ± 0.0097 s	2.05 ± 0.012 s	0.997

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 13218859263

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 95.121%

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Totals
Change from base Build 13218720464:	0.03%
Covered Lines:	3392
Relevant Lines:	3566

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💛 - Coveralls