[Kernel] Minor refactor -- add missing getters to CommitInfo + add no…

…n-null checks to constructor (delta-io#4194)

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#### Which Delta project/connector is this regarding?
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- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [x] Kernel
- [ ] Other (fill in here)

## Description

Add missing getters + requireNonNull checks.

## How was this patch tested?

Existing tests suffice.

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

No

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/CommitInfo.java

@@ -18,6 +18,7 @@
 import static io.delta.kernel.internal.DeltaErrors.wrapEngineExceptionThrowsIO;
 import static io.delta.kernel.internal.util.Utils.singletonCloseableIterator;
 import static io.delta.kernel.internal.util.VectorUtils.stringStringMapValue;
+import static java.util.Objects.requireNonNull;
 import static java.util.stream.Collectors.toMap;
 
 import io.delta.kernel.data.ColumnVector;
@@ -125,22 +126,14 @@ public CommitInfo(
       boolean isBlindAppend,
       String txnId,
       Map<String, String> operationMetrics) {
-    this.inCommitTimestamp = inCommitTimestamp;
+    this.inCommitTimestamp = requireNonNull(inCommitTimestamp);
     this.timestamp = timestamp;
-    this.engineInfo = engineInfo;
-    this.operation = operation;
-    this.operationParameters = Collections.unmodifiableMap(operationParameters);
+    this.engineInfo = requireNonNull(engineInfo);
+    this.operation = requireNonNull(operation);
+    this.operationParameters = Collections.unmodifiableMap(requireNonNull(operationParameters));
     this.isBlindAppend = isBlindAppend;
-    this.txnId = txnId;
-    this.operationMetrics = operationMetrics;
-  }
-
-  public Optional<Long> getInCommitTimestamp() {
-    return inCommitTimestamp;
-  }
-
-  public void setInCommitTimestamp(Optional<Long> inCommitTimestamp) {
-    this.inCommitTimestamp = inCommitTimestamp;
+    this.txnId = requireNonNull(txnId);
+    this.operationMetrics = Collections.unmodifiableMap(requireNonNull(operationMetrics));
   }
 
   public long getTimestamp() {
@@ -155,6 +148,30 @@ public String getOperation() {
     return operation;
   }
 
+  public Map<String, String> getOperationParameters() {
+    return operationParameters;
+  }
+
+  public boolean getIsBlindAppend() {
+    return isBlindAppend;
+  }
+
+  public String getTxnId() {
+    return txnId;
+  }
+
+  public Optional<Long> getInCommitTimestamp() {
+    return inCommitTimestamp;
+  }
+
+  public Map<String, String> getOperationMetrics() {
+    return operationMetrics;
+  }
+
+  public void setInCommitTimestamp(Optional<Long> inCommitTimestamp) {
+    this.inCommitTimestamp = inCommitTimestamp;
+  }
+
   /**
    * Encode as a {@link Row} object with the schema {@link CommitInfo#FULL_SCHEMA}.
    *