Import swap to new namespace

[RanVaknin]

Changes

This PR does 3 things:

1. Adjusts the pom.xml's Automatic-Module-Name to point to the new namespace
2. Search and replace the old namepsace, with the new namespace:
   com.amazonaws.services.dynamodbv2.datamodeling* -> software.amazon.awssdk.mapper.dynamodb*
3. Adjusts the directory layout to match the new namespace structure:

- services-custom/dynamodb-mapper/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.java
+ services-custom/dynamodb-mapper/src/main/java/software/amazon/awssdk/mapper/dynamodb/DynamoDBMapper.java

Whats next

After this PR the state of the feature branch would be considered "Stable" and ready to start refactoring and replacing v1 usages with their v2 counterparts. See "Porting operations" section in the below roadmap

---

DDB mapper v2 roadmap

** BASE PACKAGE SETUP **
+ 1. Source verbatim port ✅
+ 2. Test verbatim port ✅
3. Namespace swap <---- current PR
    
** PORTING OPERATIONS **
1. load()
2. save()
3. query() + scan()
4. deleteItem()
5. updateItem()
6. Batch operations
7. Transactions
8. Misc

** PERFORMANCE IMPROVEMENTS **
1. getTableModel caching
2. Wire "fast" createX AV factory methods to convertors
3. ByteBuffer → SdkBytes copy
4. Others

** DEPENDENCY MODERNIZATION **
1. EasyMock -> Mockito
2. Log4j 1.x -> 2.x
3. commons-logging -> SLF4J

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