Previously, messages and notes that had multiple lines (via `<br>`-tags) were only displayed correctly
when using the default `center` value for the `messageAlign` and `noteAlign` configuration options.
Using `left` or `right` for the alignment options caused the text to collapse and become illegible,
as outlined in issue #3011.
This comes as a side-effect from how the internal `valign` text-rendering option was configured for
messages and notes:
```js
// Example from `sequenceRenderer.js: drawMessage()`
textObj.anchor = conf.messageAlign;
textObj.valign = conf.messageAlign;
```
Both the `anchor` option (which controls left-right alignment) and the `valign` option (which controls
vertical top-down placement) were set to the same value, the user-provided `messageAlign` config option.
While `left` and `right` are valid values for the `anchor` option, they were effectively no-ops for the
`valign` option, which only supports `top`, `start`, `middle`, `center`, `bottom`, and `end`.
To fix the issue, the `valign` property is now always set to `center` for notes and messages.
Similarly, the `dominantBaseline` option of texts is now always set to `middle`, rather than setting it to
either `text-{before,after}-edge`, which caused left-aligned multi-line text to always be "top-left" aligned
inside a note (or "bottom-right" when attempting to right-align).
Now, texts in messages and notes are always vertically centered and alignment options correctly apply for
both single and multi-line content.
