ICU-21480 BRS69 ICU4J API signature file

- Supplied missing API comment to com.ibm.icu.nubmer.Precision#trailingZeroDisplay(TrailingZeroDisplay)
- Generated API signature file for ICU4J 69.1 and added to the repository
- Delete ICU4J 59 API signature file
- Deleted unused icu4j/eclipse-build/build.properties. The folder eclipse-build was deleted, but someone worked on ICU version seemed to add it back again. Delete it again.

icu4j/eclipse-build/build.properties

@@ -1,9 +0,0 @@
-# Copyright (C) 2016 and later: Unicode, Inc. and others.
-# License & terms of use: http://www.unicode.org/copyright.html
-#*******************************************************************************
-#* Copyright (C) 2010-2016, International Business Machines Corporation and    *
-#* others. All Rights Reserved.                                                *
-#*******************************************************************************
-icu4j.plugin.impl.version.string=69.1.0
-copyright.eclipse=(C) 2016 and later: Unicode, Inc. and others. License & terms of use: http://www.unicode.org/copyright.html
-icu4j.data.version.number=69

icu4j/main/classes/core/src/com/ibm/icu/number/Precision.java

@@ -339,6 +339,13 @@ public abstract class Precision {
         }
     }
 
+    /**
+     * Configure how trailing zeros are displayed on numbers. For example, to hide trailing zeros
+     * when the number is an integer, use HIDE_IF_WHOLE.
+     *
+     * @param trailingZeroDisplay Option to configure the display of trailing zeros.
+     * @draft ICU 69
+     */
     public Precision trailingZeroDisplay(TrailingZeroDisplay trailingZeroDisplay) {
         Precision result = this.createCopy();
         result.trailingZeroDisplay = trailingZeroDisplay;