Default to in-memory OPcache on PHP 8.1-8.4 (about 2x faster journeys than OPcache off) #2581

What happened

#2574 turned OPcache off by default, because php-wasm's default mode, file-cache-only, is slower than compiling every script. That change only measured the file cache.

In-memory OPcache (opcache.file_cache_only = 0) is a lot faster. On the Extra Chill network rig (27 plugins, 11-site multisite, PHP 8.4), Extra-Chill/extrachill#483 set it through pluginRuntime.php.bootstrapIniEntries. Journey step times, against 14 baseline runs with OPcache off:

A probe at the end of the run reported OPcache enabled: 7,964 hits, 4,390 misses, 0 out-of-memory or hash restarts, 125 MB used.

Target state

• With no recipe override, the bootstrap php.ini turns on in-memory OPcache for PHP 8.1–8.4: opcache.enable=1, enable_cli=1, file_cache_only=0, memory_consumption=256, interned_strings_buffer=16, max_accelerated_files=20000, revalidate_freq=0.
• PHP 7.4, 8.0 and 8.5 keep OPcache off. Enable in-memory OPcache for PHP 8.1+ to reduce warm request latency WordPress/wordpress-playground#3617 found in-memory OPcache crashes 7.4/8.0 and misbehaves on 8.5.
• Recipe bootstrapIniEntries still override the default.
• Extend tests/playground-cli-runner-bootstrap-ini.test.ts with the version matrix.

Once this ships, Extra-Chill/extrachill can drop its rig-side override.

🤖 Filed by Extra Chill Bot (Claude) on Chris's behalf.