Add support for lazy_builders and dynamic page cache

Re-rolled the patch against the latest 4.8 tagged release. Also included changes from #2849867 📌 Custom attributes in panels blocks and variants Fixed , by added the required changes to the new PanelsBlockViewBuilder::buildPreRenderableBlock().

Tested the patch and seems to work as expected. On my search page based on panels, I now get two additional entries in the cache_render table for panel_block:

-----------------------------------------------------------------------------------------------+------------+
| cid                                                                                                                  | expire     |
+--------------------------------------------------------------------------------------------------------+------------+
| panels_block:29fd4183-c02c-4ac4-9d8e-8e99ed1bd57f:[languages:language_content]=en:[languages:language_interface]=en:[languages:language_url]=en:[route]=page_manager.page_view_search_search-panels_variant-035786c7EzDnDb5LJABAW5Gfv6h4fZJLlJps3jAE6d18HCRgQ_M |         -1 |
| panels_block:29fd4183-c02c-4ac4-9d8e-8e99ed1bd57f:[languages:language_content]=en:[languages:language_interface]=en:[theme]=gcext_wxt:[url]=https://EXAMPLE.ca/en/search/site:[user.node_grants:view]=view.alOpv5-PurEF5Wj1lM1tRCLhW0OhmHwrTkZxw64Z6l4Uo                                              |         -1 |

I also get two additional entries in the cache_dynamic_page_cache table with page_manager in the route:

-------------------------------------------------------------------------------------------+--------+
| cid                                                                                                 | expire |
+-----------------------------------------------------------------------------------------+--------+
| response:[languages]=en,en:[request_format]=html:[route]=page_manager.page_view_search_search-panels_variant-035786c7117b4e38d0f169239752ce71158266ae2f6e4aa230fbbb87bd699c0e3:[theme]=gcext_wxt:[url]=https://hcdev3_25TRRLA6Usnws7GjYEELUBQ3fVNz42kU0SRvdTV0I           |       -1 |
| response:[request_format]=html:[route]=page_manager.page_view_search_search-panels_variant-035786c7117b4e38d0f169239752ce71158266ae2f6e4aa230fbbb87bd699c0e3                                                                                                    |            -1 |

joseph.olstad → made their first commit to this issue’s fork.

rolled patch #40 into MR25

Patch #40 and MR 25 diff are identical.