[REF] Remove old require_once statements made obsolete by autoloader

[colemanw]

Overview

Removes unnecessary code leftover from PHP 4.

Technical Details

All of these require_once are requiring classes beginning with CRM_, which is definitely handled by our autoloader.

[civibot]

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[totten]

Agree these statements look like they should work with the autoloader.

Most of these changes probably get some kind of coverage via unit-tests, although unit-tests are slightly unrepresentative (because classloading is generally done once-per-suite rather than once-per-use-case). So I did some light r-run that touched a few of these (eg use some admin screens with getIdAndAction; eg use an exporter). Worked well.

Merging.