test: migrate math/base/special/trigamma to ULP-based testing

[ujjwalv01]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• Migrates the unit tests for math/base/special/trigamma (test.js and test.native.js) from relative tolerance testing to ULP difference testing using @stdlib/assert/is-almost-same-value.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352

Questions

Any questions for reviewers of this pull request?

No.

Other

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Implementation Note on ULP Tolerances:
When initially testing with a 1 ULP tolerance across all test loops, 251 out of 4,105 test cases failed (2 cases in the positive number loop and 249 cases in the negative number loop).

Because trigamma relies on rational Chebyshev approximations and asymptotic expansions—particularly in negative regions where reflection formulas are evaluated—slight rounding differences naturally accumulate. To strictly adhere to Instruction #4 of RFC #11352 ("Make sure that you put the minimum required ULP value possible"), the tolerances were set to:

• 2 ULPs for positive numbers (positive.json fixture)
• 3 ULPs for negative numbers (negative.json fixture)

These bounds represent the exact mathematical floor required to achieve a 100% pass rate (4,105 / 4,105 passing) while keeping the accuracy budget as tight as possible.

Checklist

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• Read, understood, and followed the contributing guidelines.

AI Assistance

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Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/trigamma	$\\color{green}558/558$ $\\color{green}+100.00\\%$	$\\color{green}71/71$ $\\color{green}+100.00\\%$	$\\color{green}7/7$ $\\color{green}+100.00\\%$	$\\color{green}558/558$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.