PHOENIX-7524 Resolve character encoding mismatch by enforcing UTF-8 in sqlline.py

[mouhibrealme]

The issue with certain characters, such as Japanese, Polish, and other non-ASCII characters, being exported incorrectly has been resolved. The root cause was an encoding mismatch, where character data was not properly handled in the java_cmd command in sqlline.py. This command constructs and executes a Java process to launch SQLLine, a command-line tool for executing SQL queries against Apache Phoenix.

To address this, the sqlline.py file was modified to explicitly enforce UTF-8 encoding.

This ensures that all character data is correctly encoded and exported, preventing data corruption or misinterpretation due to incorrect encoding settings.