Accept updated version of DPDD (LSE-163)

I propose to baseline a new version of the DPDD, incorporating updates from the following tickets:

• DM-10540, which fixes numerous references to outdated "Level 1"/"Level 2" terminology and clarifies that Prompt Products include all of the result of nightly processing, rather than exclusively associating it with image differencing products (which are generated on both nightly and annual cadences). This also improves some of the description around image differencing during data release production (DRP does image differencing, but it's sufficiently distinct that it's not a "reprocessing" of the PPDB), and removes outdated references to a "living" PPDB vs old PPDBs that are archived. "Level 1 Database" is replaced throughout with "Prompt Products Database".
• DM-15671 fixes some statements in Section 1.2 that over-simplified the image processing stages, and uses LDM-151-consistent terminology to refer to the single frame processing pipeline rather than the "ISR pipeline".
• DM-16688 fixes inconsistent abbreviations of arcseconds as a unit in the DPDD table schemas.
• DM-15784 removes a statement that MOPS will delete DIAObjects if they are found to be SSObjects; the DIAObjects should persist but will be marked as superseded.

The proposed version incorporating all of these tickets can be viewed at https://lse-163.lsst.io/v/DM-10540/index.html. New or changed text is in blue, removed text is in red. The highlighting includes some changes from a prior RFC which have yet to be approved by project CCB. This update will also have to be sent to project CCB for approval.