Add declarative config support for view unit (#7942)

Author: jack-berg

sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/fileconfig/InstrumentSelectorFactory.java

@@ -37,6 +37,9 @@ public InstrumentSelector create(ViewSelectorModel model, DeclarativeConfigConte
       }
       builder.setType(instrumentType);
     }
+    if (model.getUnit() != null) {
+      builder.setUnit(model.getUnit());
+    }
     if (model.getMeterName() != null) {
       builder.setMeterName(model.getMeterName());
     }

sdk-extensions/incubator/src/test/java/io/opentelemetry/sdk/extension/incubator/fileconfig/InstrumentSelectorFactoryTest.java

@@ -35,6 +35,7 @@ void create() {
                     new ViewSelectorModel()
                         .withInstrumentName("instrument-name")
                         .withInstrumentType(ViewSelectorModel.InstrumentType.COUNTER)
+                        .withUnit("ms")
                         .withMeterName("meter-name")
                         .withMeterSchemaUrl("https://opentelemetry.io/schemas/1.16.0")
                         .withMeterVersion("1.0.0"),
@@ -43,6 +44,7 @@ void create() {
             InstrumentSelector.builder()
                 .setName("instrument-name")
                 .setType(InstrumentType.COUNTER)
+                .setUnit("ms")
                 .setMeterName("meter-name")
                 .setMeterSchemaUrl("https://opentelemetry.io/schemas/1.16.0")
                 .setMeterVersion("1.0.0")