Initialize aria-pressed for toggle buttons

[Kevinjohn]

Toggle buttons initialized without aria-pressed are not exposed as toggle buttons to assistive technologies until their first activation.

Description

• Initialize a missing aria-pressed value from the button's current .active state.
• Preserve an explicit author-provided aria-pressed value.
• Cover inactive, pre-active, and explicitly configured buttons with a regression test.

Motivation & Context

Fixes #42328.

Observable sequence:

• Create inactive and pre-active elements with data-bs-toggle="button".
• Initialize the Button plugin for each element.
• Expected: aria-pressed="false" and aria-pressed="true", matching each element's initial state.
• Actual: both attributes remain absent until the button is toggled.

This replaces #42466 with a focused change based on current main and expands coverage for explicit author-provided values.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using pnpm run js-lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Actual screenshots

Before (current main): the regression test receives null instead of the expected initial ARIA state.

After (this PR): the same Chrome Headless run reports 810/810 successful tests.

Validation

• pnpm exec karma start js/tests/karma.conf.js --single-run: 810/810 successful
• pnpm run js-lint: passes with 18 pre-existing warning-comment warnings
• git diff --check

The local Karma process prints its existing full-page-reload shutdown warning after the test result.

Related issues

• Fixes Missing aria-pressed="false" at toggle buttons initialization (button plugin) #42328
• Replaces Fix aria-pressed initialization for toggle buttons #42466