LIMS-2135: Update PHP Libraries

[ndg63276]

JIRA ticket: LIMS-2135

Summary:

Various PHP libraries can be updated

Changes:

• Tell Composer we are using PHP 7.4.33 which is on production
• Remove the getallheaders polyfill, and then add a bootstrapped version for CI testing
• Remove the bcmath polyfill, but enforce the native library instead
• Increment the major version of php-amqplib and psalm
• Allow minor updates on htmlpurifier, sql-formatter, mpdf, slim, and zipstream-php
• Change how JWTs are decoded in php-jwt 6 with PHP 7.4.33
• Fix some tests that now fail as PHP 7.4 is tougher on TypeErrors

Not done:

• No change to phpcas as that may be removed soon
• No major update to slim as that would require large changes

To test:

• Use the production database, and retrigger a processing job, to check the php-amqplib update
• Open a shipment and click "Print Shipment Labels" to check the mpdf update
• Run ./vendor/bin/psalm within the container, check no errors occur