CLDR-18464 Add a Before Hijrah era to the Islamic calendars

See #4581

Author: sffc

common/main/en.xml

@@ -3195,8 +3195,13 @@ annotations.
 					</monthContext>
 				</months>
 				<eras>
+					<eraNames>
+						<era type="0">Anno Hegirae</era>
+						<era type="1">Before Hijrah</era>
+					</eraNames>
 					<eraAbbr>
 						<era type="0">AH</era>
+						<era type="1">BH</era>
 					</eraAbbr>
 				</eras>
 				<dateFormats>

common/main/root.xml

@@ -1856,6 +1856,7 @@ Warnings: All cp values have U+FE0F characters removed. See /annotationsDerived/
 					</eraNames>
 					<eraAbbr>
 						<era type="0">AH</era>
+						<era type="1">BH</era>
 					</eraAbbr>
 					<eraNarrow>
 						<alias source="locale" path="../eraAbbr"/>

common/supplemental/supplementalData.xml

@@ -4536,30 +4536,35 @@ XXX Code for transations where no currency is involved
           <calendarSystem type="lunar" />
           <eras>
               <era type="0" start="622-7-15" code="islamic" aliases="ah"/>
+              <era type="1" end="622-7-14" code="islamic-inverse" aliases="bh"/>
           </eras>
         </calendar>
         <calendar type="islamic-civil">
           <calendarSystem type="lunar" />
           <eras>
               <era type="0" start="622-7-16" code="islamic-civil" aliases="islamicc ah"/>
+              <era type="1" end="622-7-15" code="islamic-civil-inverse" aliases="bh"/>
           </eras>
         </calendar>
         <calendar type="islamic-rgsa">
           <calendarSystem type="lunar" />
           <eras>
               <era type="0" start="622-7-15" code="islamic-rgsa" aliases="ah"/>
+              <era type="1" end="622-7-14" code="islamic-rgsa-inverse" aliases="bh"/>
           </eras>
         </calendar>
         <calendar type="islamic-tbla">
           <calendarSystem type="lunar" />
           <eras>
               <era type="0" start="622-7-15" code="islamic-tbla" aliases="ah"/>
+              <era type="1" end="622-7-14" code="islamic-tbla-inverse" aliases="bh"/>
           </eras>
         </calendar>
         <calendar type="islamic-umalqura">
           <calendarSystem type="lunar" />
           <eras>
               <era type="0" start="622-7-15" code="islamic-umalqura" aliases="ah"/>
+              <era type="1" end="622-7-14" code="islamic-umalqura-inverse" aliases="bh"/>
           </eras>
         </calendar>
         <calendar type="chinese">