[SPARK-52369] Fix Session ID to be lowercased always

### What changes were proposed in this pull request?

This PR aims to fix `SparkSession` to make `Session ID` lowercased always.

### Why are the changes needed?

Apache Spark handles `SessionID` in a case sensitive way and assumes lowercases always.

### Does this PR introduce _any_ user-facing change?

Yes, previously, the user-given Session ID might be mismatched due to the case-sensitivity.

### How was this patch tested?

Pass the CIs.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#188 from dongjoon-hyun/SPARK-52369.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

Sources/SparkConnect/SparkSession.swift

@@ -44,9 +44,9 @@ public actor SparkSession {
     self.client = SparkConnectClient(remote: connection)
     // Since `Session ID` belongs to `SparkSession`, we handle this here.
     if connection.contains(regexSessionID) {
-      self.sessionID = connection.firstMatch(of: regexSessionID)!.1.uppercased()
+      self.sessionID = connection.firstMatch(of: regexSessionID)!.1.lowercased()
     } else {
-      self.sessionID = UUID().uuidString
+      self.sessionID = UUID().uuidString.lowercased()
     }
     self.conf = RuntimeConf(self.client)
   }