Start a 2.0.x branch to support Drupal 10 and update all use of deprecation in the Ace Code Editor module

Problem/Motivation

Drupal 10.0 development

Following with

The current composer require status for this module under Drupal 10

composer create-project drupal/recommended-project:10.0.0-alpha4@alpha /var/www/html/sandboxes/drupal10ace_editor
cd /var/www/html/sandboxes/drupal10ace_editor/

composer config minimum-stability dev

composer config repositories.assets composer https://asset-packagist.org
composer config --json extra.installer-types '["npm-asset", "bower-asset"]'
composer config --json extra.installer-paths.web\/libraries\/ace '["npm-asset/ace-builds"]'
composer config --unset extra.installer-paths.web\/libraries\/\{\$name\}
composer config --json extra.installer-paths.web\/libraries\/\{\$name\} '["type:drupal-library", "type:bower-asset", "type:npm-asset"]'

composer require drupal/ace_editor;

is having the following problem

Using version ^1.3 for drupal/ace_editor
./composer.json has been updated
Running composer update drupal/ace_editor
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires drupal/ace_editor ^1.3 -> satisfiable by drupal/ace_editor[1.3.0, 1.x-dev].
    - drupal/ace_editor[1.3.0, ..., 1.x-dev] require drupal/core ^8.8 || ^9 -> found drupal/core[8.8.0-alpha1, ..., 8.9.x-dev, 9.0.0-alpha1, ..., 9.5.x-dev] but the package is fixed to 10.0.0-alpha4 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
You can also try re-running composer require with an explicit version constraint, e.g. "composer require drupal/ace_editor:*" to figure out if any version is installable, or "composer require drupal/ace_editor:^2.1" if you know which you need.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

Proposed resolution

• Add a 2.0.x branch
• Change to core_version_requirement: ^8.8 || ^9 || ^10 in the ace_editor.info.yml file
• Release a 2.0.x-dev development version
• Change all deprecated packages, classes, functions, asset libraries to the Drupal 10 way

Further drupal-check on

cd /var/www/html/sandboxes/drupal10ace_editor

composer config minimum-stability dev

composer require mglaman/drupal-check --dev
composer require phpspec/prophecy-phpunit:^2 --dev 

Output:

ace_editor--drupal-check--report.txt

Remaining tasks

• ✅ Add a 2.0.x branch
• ✅ Change to core_version_requirement: ^8.8 || ^9 || ^10 in the ace_editor.info.yml file
• ✅ Release a 2.0.x-dev development version
• ✅ This will ease the work on further issues
• ✅ Real physical testing with Drupal ~10
• ✅ drupal-check on the code
• ✅ Testing to ensure no regression
• ✅ Full testing and approval
• ➖ Automated functional testing coverage

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A