Reduce RAM usage and periodically flush cache / garbage collection

[sypets]

• RAM allocation via usage of TransientMemoryBackend within internal core functions called by isRecordsOnPageShouldBeChecked should be reduced
  • PR [BUGFIX] Flush runtime cache periodically in LinkAnalyzer #484 by @mikelwohlschlegel to periodically flush TransientMemoryBackend
• improve efficiency of isRecordsOnPageShouldBeChecked
  • possibly get rid of the function isRecordsOnPageShouldBeChecked or some functionality by performing the checks in PagesRepository::getPageList => however some checks should be performed in pages (e.g. for doktype = 3 and doktype=4 but not for records), but could be
  • be careful: is not called for table pages, is only called for other records, should maybe do pages first or store result in $this->pids
  • do not make this so complicated => some of the content which should not be checked should not really exist in the first place (e.g. tt_content on doktype = 3 or doktype = 4
  • alternative: make isRecordsOnPageShouldBeChecked configurable (it seems pretty resource-hungry and is of little value)
  • instead of fetching each page, already do a join with pages on fetching records
• (handle in separate issue!) in BE do not fetch all broken links (and paginate the entire array), fetch only max. 100 at a time
  • see PR WIP: fetch only one page in DB when paginating, not entire list #472