chore: use testcontext for issues-*.js tests

[Uzlopak]

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[Copilot]

Pull Request Overview

This PR migrates issue-related test files from using the external @matteo.collina/tspl testing library to Node.js's built-in test context. The migration involves replacing tspl() initialization patterns with native test context methods and updating assertion calls to use the t.assert API.

Key changes:

• Removes dependency on @matteo.collina/tspl library
• Converts async test functions to callback-based tests using done()
• Updates all assertion calls to use t.assert.* methods

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/issue-810.js	Converts 4 tests from tspl to native test context with callback pattern
test/issue-803.js	Migrates single large file test from tspl to callback-based test
test/issue-4244.js	Updates assert import to use test context assertions
test/issue-3959.js	Adds test context parameter and updates assertion calls
test/issue-3934.js	Removes assert import and updates to test context assertions
test/issue-3904.js	Migrates forEach test loop to use test context parameter
test/issue-3410.js	Converts tspl tests to native test context with plan()
test/issue-3356.js	Updates async test from tspl to test context assertions
test/issue-2590.js	Migrates abort controller tests from tspl to test context
test/issue-2349.js	Converts stream test to async with test context
test/issue-2283.js	Updates FormData tests to use test context assertions
test/issue-2078.js	Migrates MockPool test from tspl to test context
test/issue-2065.js	Updates FormData content-length test to test context
test/issue-1757.js	Migrates dispatcher test to use test context assertions

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