### Bug description

## Description

The behaviour of `abstract-title` is not consistent with other metadata labels. Other labels like `author-title` and `published-title` can be specified under `format` *or* the top level of a document, but `abstract-title` only works when specified at the top level. As a consequence you can't provide your own abstract title in Quarto extensions.

The expected behaviour is that the abstract title should be "My Abstract" in both examples below.

## Reprex

Here the abstract title remains as "Abstract":

```qmd
---
title: "Reprex"
author: First Last
date: 2023-01-09
abstract: Some abstract text
format:
  html:
    author-title: My Author
    published-title: My Date
    abstract-title: My Abstract
---

Some body text
```

Here the abstract changes to "My Abstract":

```qmd
---
title: "Reprex"
author: First Last
date: 2023-01-09
abstract: Some abstract text
format:
  html:
    author-title: My Author
    published-title: My Date
abstract-title: My Abstract
---

Some body text
```

### Checklist

- [X] Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
- [X] Please [format your issue](https://quarto.org/bug-reports.html#formatting-make-githubs-markdown-work-for-us) so it is easier for us to read the bug report.
- [ ] Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
- [ ] Please document the operating system you're running. If on Linux, please provide the specific distribution.
2023-01-10T00:49:33Z
mccarthy-m-g
bug
closed
Inconsistent behaviour providing your own `abstract-title` metadata label
https://github.com/quarto-dev/quarto-cli/issues/3911