feat: add blas/ext/base/gtriu

[MeKaustubh07]

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Resolves #{{TODO: add issue number}}.

Description

What is the purpose of this pull request?

This pull request:

• feat: add blas/ext/base/gtriu

Related Issues

Resolves #13550

This pull request has the following related issues:

• #{{TODO: add related issue number}}

Questions

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No.

Other

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No.

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• Read, understood, and followed the contributing guidelines.

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{{TODO: add disclosure if applicable}}

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/gtriu	$\\color{green}439/439$ $\\color{green}+0.00\\%$	$\\color{green}37/37$ $\\color{green}+0.00\\%$	$\\color{green}4/4$ $\\color{green}+0.00\\%$	$\\color{green}439/439$ $\\color{green}+0.00\\%$

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

[kgryte]

@MeKaustubh07 You have done a number of these blas/ext/base/g* packages. I shouldn't have to be cleaning up your tests at this point. Don't take shortcuts. The code coverage report should have been enough of an indication that your tests were incomplete.

[kgryte]

@MeKaustubh07 Now that we have added gtriu, you can add blas/ext/base/gtril (copying the lower triangular part and where k semantics flip with elements above the specified diagonal ignored).

You can also go ahead and add

blas/ext/base/dtriu
blas/ext/base/striu
blas/ext/base/ctriu
blas/ext/base/ztriu