Issue #3420997 by sorlov, quietone, DanielVeza, smustgrave, alexpott, mstrelan: Convert MediaSource plugin discovery to attributes

Issue #2831274 by slashrsm, seanB, Wim Leers, chr.fritsch, phenaproxima, naveenvalecha, marcoscano, webflo, Gábor Hojtsy, amateescu, Boobaa, iMiksu, mtodor, effulgentsia, xjm, Berdir, tim.plunkett, dawehner, tkoleary, tstoeckler, tedbow, alexpott, yoroy, catch, Bojhan, andypost, jhedstrom, jibran, aspilicious, boztek, cbr, bigbaldy, alex0412, dagmar, blueminds, ekes, Dave Reid, Sam152, bojanz, pixelmord, jonathanshaw, CTaPByK, webchick, samuel.mortenson, dbt102, dishabhadra, proweb.ua, rakesh.gectcr, rasikap, paranojik, pameeela, neardark, NormySan, Primsi, nicolas.rafaelli, romainj, royal121, vladan.me, vpeltot, woprrr, vilepickle, toni04, scheban, tduong, temkin, tim-e, mbovan, mashermike, felribeiro, giancarlosotelo, hctom, euphoric_mv, eric.duran7@gmail.com, edurenye, eelkeblok, H1ghlander, Jaesin, hkirsman, ja_ca, NickWilde, joachim, joshi.rohit100, marcingy, NerOcrO, Mixologic, jcisio, jfrederick, Lukas von Blarer, Maouna: Bring Media entity module to core as Media module

Issue #2719695 by alexpott, Mile23: Fix 'Drupal.Classes.ClassDeclaration.CloseBraceAfterBody' coding standard

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2318281 by tim.plunkett, dawehner | kim.pepper: Provide a standard way to check a plugin is an instance of the required interface.

Issue #2087965 by AndyThornton, neclimdul, tim.plunkett, jhodgdon, pwolanin: Fixed The SearchPluginManager needs to provide an alter hook for its discovery.

Issue #2053153 by tim.plunkett, dawehner, damiankloip, aspilicious: Allow contrib modules to provide plugins on behalf of optional modules.

Issue #2042807 by tim.plunkett, pwolanin, ianthomas_uk, jhodgdon: Convert search plugins to use a ConfigEntity and a PluginBag.

Issue #2003482 by pwolanin, jhodgdon, kim.pepper, Nick_vh, tim.plunkett, jibran, Berdir, effulgentsia, alexpott: Convert hook_search_info() to plugin system.