Improve accessibility of toggle buttons with contextual aria-labels

[Ankita19Rathore]

What this PR does

This pull request improves the accessibility of the "Toggle more information"
buttons used in the HTML output by making their aria-labels contextual and
descriptive.

---

What was happening before

Previously, all toggle buttons were created using the following aria-label:

aria-label="Toggle more information"

Because this same label was used everywhere, screen readers announced
multiple buttons with identical text. This made it difficult for users
to understand what each toggle button would expand or control.

---

What was changed

The build_toggler() method was updated to accept an optional $context
parameter.

Before:

protected static function build_toggler() {
	$out = '<button class="qm-toggle" ... aria-label="Toggle more information">...</button>';
	return $out;
}

After:

protected static function build_toggler( $context = '' ) {
	$label = __( 'Toggle more information', 'query-monitor' );

	if ( $context ) {
		$label = sprintf(
			__( 'Toggle more information about %s', 'query-monitor' ),
			$context
		);
	}

	return '<button class="qm-toggle" ... aria-label="' . esc_attr( $label ) . '">...</button>';
}

Behavior after this change

If context is provided, the aria-label becomes descriptive
(e.g. Toggle more information about Jetpack hook callback).

If no context is provided, the original behavior is preserved.

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Why this change is important

Screen reader users rely on aria-labels to understand interactive elements.
Using repeated generic labels reduces accessibility and usability.

By introducing contextual aria-labels, each toggle button can now be
clearly distinguished, aligning with accessibility best practices.

---

Scope and safety of change

• The change is limited to the build_toggler() method only.
• No visual or functional behavior has been altered.
• Existing functionality remains backward-compatible.
• No unrelated code was modified.

---

[Ankita19Rathore]

I have fixed the issue mentioned above.
Please review the changes.

[johnbillion]

Thanks for the PR @Ankita19Rathore . I'll take a look soon.

[Ankita19Rathore]

Thanks for the review!