Improve typing / validation / tests in `Html::renderTagAttributes()`

[arogachev]

Such structure is not guaranteed:

html/src/Html.php

Line 1625 in c678843

/** @psalm-var array<array-key, array|string|\Stringable|null> $value */

html/src/Html.php

Line 1638 in c678843

/** @psalm-var array<string,string> $value */