"Found unconstructed IntlDateFormatter" when logging happens during upgrade:db on PHP 8.1.26

# Environments:
Ubuntu 20.04, Ubuntu 22.04
PHP 8.1.26 (CLI and PHP-FPM)
cv 0.3.48
/etc/php/8.1/cli/php.ini sets `intl.default_locale = en_US` or `en_US.utf8` or that line is commented out
Drupal 9.5.11, WordPress 6.4.2

# Steps to reproduce:
- Have a Civi install before 5.66 (5.64.4 in this case)
- Upgrade to 5.66.2 or later (5.68.0 in this case)
- Run `cv upgrade:db`

# Results:
If the upgrader tries to log something as the FiveSixtySix step does, the upgrade fails with "Found error IntlDateFormatter" in php-8.1-strftime.php line 105.

Importantly: Restoring from a backup and running the database upgrade from the web UI works fine.

Full output of `cv upgrade:db -vvv --retry`:

```
Box Requirements Checker
========================

> Using PHP 8.1.26
> PHP is using the following php.ini file:
/etc/php/8.1/cli/php.ini

> Checking Box requirements:
✔ The application requires a version matching ">=7.3.0".
✔ The application requires the extension "json".
✔ The package "psy/psysh" requires the extension "json".
✔ The package "nikic/php-parser" requires the extension "tokenizer".
✔ The package "psy/psysh" requires the extension "tokenizer".


[OK] Your system is ready to run the application.

[BootTrait:debug] Start
[BootTrait:debug] Attempting to set verbose error reporting
[BootTrait:debug] Call standard cv bootstrap
[Bootstrap:debug] Options: {
"dynamicSettingsFile": "phar:///usr/local/bin/cv/lib/settings_location.php",
"env": "CIVICRM_SETTINGS",
"prefetch": true,
"settingsFile": null,
"search": true,
"cmsType": null,
"httpHost": "",
"output": {}
}
[Bootstrap:debug] Find settings file
[Bootstrap:debug] Load supplemental configuration for "/srv/www/d9_test/web/sites/default/civicrm.settings.php"
[Bootstrap:notice] Find CMS root for "/srv/www/d9_test"
[Bootstrap:notice] Found "drupal" in "/srv/www/d9_test/web"
[Bootstrap:notice] Simulate web environment in CLI
[Bootstrap:debug] Load settings file "/srv/www/d9_test/web/sites/default/civicrm.settings.php"
[Bootstrap:notice] Initialize class loader
[Bootstrap:notice] Call core bootstrap
[Bootstrap:debug] Finished
[BootTrait:debug] Call core bootstrap
[BootTrait:debug] Call CMS bootstrap
[BootTrait:debug] Set active MySQL timezone
[BootTrait:debug] Finished
Found CiviCRM database version 5.66.alpha1.upgrade.
Found CiviCRM code version 5.68.0.
Resuming upgrade...
Executing upgrade...
Add fields to civicrm_mail_settings to allow more flexibility for email to activity (CRM_Upgrade_Incremental_php_FiveSixtySix::addMailSettingsFields())

In php-8.1-strftime.php line 105:

[Error]
Found unconstructed IntlDateFormatter

Exception trace:
at /srv/www/d9_test/vendor/pear/log/php-8.1-strftime.php:105
IntlDateFormatter->format() at /srv/www/d9_test/vendor/pear/log/php-8.1-strftime.php:105
PHP81_BC\{closure}() at /srv/www/d9_test/vendor/pear/log/php-8.1-strftime.php:204
PHP81_BC\{closure}() at n/a:n/a
preg_replace_callback() at /srv/www/d9_test/vendor/pear/log/php-8.1-strftime.php:185
PHP81_BC\strftime() at /srv/www/d9_test/vendor/pear/log/Log.php:887
Log->formatTime() at /srv/www/d9_test/vendor/pear/log/Log/display.php:171
Log_display->log() at /srv/www/d9_test/vendor/pear/log/Log.php:375
Log->info() at /srv/www/d9_test/vendor/civicrm/civicrm-core/CRM/Upgrade/Incremental/php/FiveSixtySix.php:94
CRM_Upgrade_Incremental_php_FiveSixtySix::addMailSettingsFields() at /srv/www/d9_test/vendor/civicrm/civicrm-core/CRM/Queue/Task.php:101
CRM_Queue_Task->run() at phar:///usr/local/bin/cv/src/Util/ConsoleQueueRunner.php:44
Civi\Cv\Util\ConsoleQueueRunner->runAll() at phar:///usr/local/bin/cv/src/Command/UpgradeDbCommand.php:105
Civi\Cv\Command\UpgradeDbCommand->execute() at phar:///usr/local/bin/cv/vendor/symfony/console/Command/Command.php:127
Cvphar\Symfony\Component\Console\Command\Command->run() at phar:///usr/local/bin/cv/vendor/symfony/console/Application.php:637
Cvphar\Symfony\Component\Console\Application->doRunCommand() at phar:///usr/local/bin/cv/vendor/symfony/console/Application.php:190
Cvphar\Symfony\Component\Console\Application->doRun() at phar:///usr/local/bin/cv/src/Application.php:67
Civi\Cv\Application->doRun() at phar:///usr/local/bin/cv/vendor/symfony/console/Application.php:101
Cvphar\Symfony\Component\Console\Application->run() at phar:///usr/local/bin/cv/src/Application.php:33
Civi\Cv\Application::main() at phar:///usr/local/bin/cv/bin/cv:28
require() at /usr/local/bin/cv:14

upgrade:db [--out OUT] [--flat [FLAT]] [--dry-run] [--retry] [--skip] [--step] [--level LEVEL] [--hostname HOSTNAME] [-t|--test] [-U|--user USER]
```

# Notes & Observations
This seems related to the recent [changes in PHP 8.1.25 / PHP 8.1.26](https://github.com/php/php-src/issues/12912) around IntlDateFormatter not accepting an invalid $locale parameter. Adding some debug code to vendor/pear/log/php-8.1-strftime.php, I found that $locale is set to "C". [In 8.0,](https://www.php.net/manual/en/migration80.incompatible.php) "The default locale on startup is now always 'C'. No locales are inherited from the environment by default."

I tried rebuilding cv after adding the following to lib/src/Util/BootTrait.php's _boot_full at line 152:

```
$locale = \Civi\Core\Locale::detect();
print_r($locale);
$locale->apply();
setlocale(LC_ALL, $locale->nominal)
```

This shows the Locale object as
```
(
[nominal] => en_US
[ts] => en_US
[db] =>
[moneyFormat] => en_US
[uf] => en_US
)
```
but $locale passed to \PHP81_BC::strftime remains "C" and the error persists, so that wasn't the way to go.

Start with vendor/pear/log/php-8.1-strftime.php at line 105 and trace the logging call from CRM/Upgrade/Incremental/php/FiveSixtySix.php line 94 through cv's ConsoleQueueRunner. Review lib/src/Util/BootTrait.php _boot_full alongside the reported PHP 8.1 locale behavior, then run cv upgrade:db -vvv --retry. Done means the database upgrade completes when logging occurs under PHP 8.1.26.

Written by the indexing model from the issue text.