10.3 upgrade now missing status-message theme suggestions

Problem/Motivation

MessageCommand and the associated JavaScript API was added to Drupal core in 2019/Drupal 8.8.0, but was not used widely in Drupal core until 10.3.0, when the bigpipe module began using it to render messages created within bigpipe placeholders.

Because MessageCommand has not been used widely, many custom themes have not themed custom JavaScript messages.

For examples of how to override message theming, see:

core/themes/olivero/js/message.theme.js

and

core/themes/claro/js/messages.js

And the associated libraries-extend entries in those themes' .info.yml files.

Steps to reproduce

Original report:

Upgraded to 10.3 and status-message.html.twig is missing as a theme suggestion, breaking my custom theme. See screenshots.

Copied git bisect result from #24

2172d1009cec0e8f908a51fb2c99a1eb06b8b6da is the first bad commit
commit 2172d1009cec0e8f908a51fb2c99a1eb06b8b6da
Author: Alex Pott <alex.a.pott@googlemail.com>
Date:   Thu Feb 22 08:52:28 2024 +0000

    Issue #3379885 by catch, Wim Leers: Use MessagesCommand in BigPipe to remove special casing of the messages placeholder
    
    (cherry picked from commit 44c345dd9b8e2e1fb7131868a5d8b27c57e5b8e3)

 core/modules/big_pipe/big_pipe.services.yml        |  2 +-
 core/modules/big_pipe/src/Render/BigPipe.php       | 79 +++++-----------------
 .../big_pipe/tests/src/Functional/BigPipeTest.php  |  8 +--
 .../FunctionalJavascript/BigPipeRegressionTest.php |  9 ++-
 .../tests/src/Unit/Render/FiberPlaceholderTest.php |  4 +-
 .../tests/src/Unit/Render/ManyPlaceholderTest.php  |  4 +-
 6 files changed, 32 insertions(+), 74 deletions(-)

Issue: #3379885: Use MessagesCommand in BigPipe to remove special casing of the messages placeholder

First bad commit: 2172d1009cec0e8f908a51fb2c99a1eb06b8b6da

Bad commit at the relevant file: core/modules/big_pipe/src/Render/BigPipe.php

Proposed resolution