Add deprecated URIs to TEI from the extra field

[wlpotter]

In cases where a record has replaced a now-deprecated record, we add the old URIs to the replacing record's extra field with a deprecated key. These should create an idno element of @type="deprecated" (cf. https://github.com/srophe/syriaca-data/wiki/Deprecated-Records#deprecating-a-merged-record for the broader Syriaca conventions). A record may have multiple deprecated key:value pairs.

Note that we handle redirects in Gaddel by adding them to a redirects file on AWS, so this would purely be for ensuring the TEI record retains this info for provenance/documentation purposes, not for any display or functionality needs.