"Launch" Search Beta Release

What / Why

Lots of great stuff in #6569 and #6682 has effectively made production-ready search engines available. These are still a little hidden from adopters, however, because they are not yet easily discoverable.

In order to “launch” the search beta, we need to make these things default / discoverable / clearly documented.

Scope / UAT Target

• As an App Integrator, my created app’s SearchPage implementation should account for pagination (depends on #6062)
• As an App Integrator, my created app should include the DefaultTechDocsCollator in the backend, and an updated Search Page frontend that includes the techdocs type (not directly related to the beta milestone, but we get questions about this often)
• As an App Integrator, if I select postgres as my data store when running create-app, my Backstage search should default to using the PgSearchEngine implementation instead of LunrSearchEngine.

[iamEAP]

Sooooo close. Hang in there, stalebot.

[Fox32]

Beside solving paging I would also throw in possible breaking changes around the collator, decorator and search engine design:

Right now the collator provides a list of all documents that should be indexed, which can be a big amount of memory. I would recommend to switch to a stream based API where the results are streamed from the collator to the decorators and then to the search engine. That way we only hold in memory what is really required.