Add Docs per SFDO-Community/declarative-lookup-rollup-summaries #1300

[jlantz]

NOTE: This PR was AI generated using GitHub Copilot Workspace. I reviewed it but don't know enough about DLRS to technically vet the content. Please review carefully!

This pull request includes documentation updates to provide additional information on how merged records are handled by the DLRS system. The changes primarily focus on explaining the creation of scheduled items for recalculating rollups when records are merged.

Documentation updates:

• docs/Architecture/calculates.md: Added a section explaining that merged records may create scheduled items to handle recalculation at a later time due to complexity and potential conflicts during the merge process.
• docs/Installation/configuration.md: Included information about merged records creating scheduled items to ensure accurate rollup updates without performance issues during merges.
• docs/User Guide/scheduling_rollups_v2_21.md: Added a section detailing how merged records are managed by creating scheduled items to handle recalculations later, ensuring accuracy and avoiding performance issues.

Minor cleanup:

• docs/User Guide/scheduling_rollups_v2_21.md: Removed an unnecessary line at the end of a paragraph.tems for merged records.

docs/Architecture/calculates.md

Add a new section explaining that merged records may create scheduled items and why this occurs.
docs/User Guide/scheduling_rollups_v2_21.md

Add a note about the use of scheduled items for merged records.
docs/Installation/configuration.md

Add a mention of the use of scheduled items for merged records and provide guidance on handling this scenario.
For more details, open the Copilot Workspace session.

[aheber]

I think these are good additions and I was surprised at the multiple appropriate locations that it added the notes.

[aheber]

@sharicarlson13 can you get someone from the docs team to review and merge this?