Java: fixed minRelevance filtering in getNearestMatchesAsync. make ge…

…tSearc… (#3059)

### Motivation and Context
While trying to use current AzureCognitiveSearchMemoryStore I think I
found a bug in getNearestMatchesAsynch.
I had to create my own implementation extending this class in order to
test it.
Furthermore It was hard to create a custom implementation as
getSearchClient is private and I could not reuse the cognitive search
client.
For my custom implementation look here:
https://github.com/Azure-Samples/azure-search-openai-demo-java/blob/main/app/backend/src/main/java/com/microsoft/openai/samples/rag/ask/approaches/semantickernel/memory/CustomAzureCognitiveSearchMemoryStore.java


### Description

- fixed minRelevance filtering in getNearestMatchesAsync. 
- make getSearchClient protected to improve extensibility

### Contribution Checklist
<!-- Before submitting this PR, please make sure: -->
 - Maven build worked locally
- All unit tests passed locally. However I noticed the cognitive search
tests are skipped. However the same implementation has been tested in my
code repo:
https://github.com/Azure-Samples/azure-search-openai-demo-java

java/connectors/semantickernel-connectors-memory-azurecognitivesearch/src/main/java/com/microsoft/semantickernel/connectors/memory/azurecognitivesearch/AzureCognitiveSearchMemoryStore.java

@@ -215,7 +215,7 @@ public Mono<Collection<Tuple2<MemoryRecord, Float>>> getNearestMatchesAsync(
         SearchOptions searchOptions = new SearchOptions().setVectors(searchVector);
 
         return client.search(null, searchOptions)
-                .filter(result -> (double) minRelevanceScore >= result.getScore())
+                .filter(result -> (double) minRelevanceScore <= result.getScore())
                 .map(
                         result -> {
                             MemoryRecord memoryRecord =
@@ -418,7 +418,7 @@ record -> {
      * @param indexName Index name
      * @return Search client ready to read/write
      */
-    private SearchAsyncClient getSearchClient(@Nonnull String indexName) {
+    protected SearchAsyncClient getSearchClient(@Nonnull String indexName) {
         String normalizedIndexName = normalizeIndexName(indexName);
         return _clientsByIndex.computeIfAbsent(
                 normalizedIndexName, _adminClient::getSearchAsyncClient);