GH-9114: SFTP: Use canonicalPath exists operation

Fixes: #9114

If path is not in normalized presentation, the SFTP operation might fail like:
```
Caused by: SFTP error (SSH_FX_NO_SUCH_PATH): The file path does not exist or is invalid.
at org.apache.sshd.sftp.client.impl.AbstractSftpClient.throwStatusException(AbstractSftpClient.java:277)
at org.apache.sshd.sftp.client.impl.AbstractSftpClient.checkAttributesResponse(AbstractSftpClient.java:333)
at org.apache.sshd.sftp.client.impl.AbstractSftpClient.checkAttributes(AbstractSftpClient.java:325)
at org.apache.sshd.sftp.client.impl.AbstractSftpClient.lstat(AbstractSftpClient.java:1010)
at org.springframework.integration.sftp.session.SftpSession.exists(SftpSession.java:191)
```

* Use it now like this `this.sftpClient.lstat(normalizePath(path))`

(cherry picked from commit 8b88668)

Author: artembilan

spring-integration-sftp/src/main/java/org/springframework/integration/sftp/session/SftpSession.java

@@ -189,7 +189,7 @@ public boolean rmdir(String remoteDirectory) throws IOException {
 	@Override
 	public boolean exists(String path) {
 		try {
-			this.sftpClient.lstat(path);
+			this.sftpClient.lstat(normalizePath(path));
 			return true;
 		}
 		catch (SftpException ex) {

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpOutboundTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -260,17 +260,25 @@ public void testSharedSession(boolean sharedSession) throws IOException {
 	public void testExists() throws IOException {
 		SftpClient sftpClient = mock(SftpClient.class);
 
+		willReturn("/exist")
+				.given(sftpClient)
+				.canonicalPath("exist");
+
+		willReturn("/notExist")
+				.given(sftpClient)
+				.canonicalPath("notExist");
+
 		willReturn(new SftpClient.Attributes())
 				.given(sftpClient)
-				.lstat(eq("exist"));
+				.lstat("/exist");
 
 		willThrow(new SftpException(SftpConstants.SSH_FX_NO_SUCH_FILE, "notExist"))
 				.given(sftpClient)
-				.lstat(eq("notExist"));
+				.lstat("/notExist");
 
 		willThrow(new SshException(SshConstants.SSH_OPEN_CONNECT_FAILED, "Connection lost."))
 				.given(sftpClient)
-				.lstat(and(not(eq("exist")), not(eq("notExist"))));
+				.lstat(and(not(eq("/exist")), not(eq("/notExist"))));
 
 		SftpSession sftpSession = new SftpSession(sftpClient);
 

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpServerOutboundTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2022 the original author or authors.
+ * Copyright 2013-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -701,7 +701,7 @@ public void testSessionExists() throws IOException {
 		assertThatExceptionOfType(UncheckedIOException.class)
 				.isThrownBy(() -> session.exists("any"))
 				.withRootCauseInstanceOf(IOException.class)
-				.withStackTraceContaining("lstat(any) client is closed");
+				.withStackTraceContaining("canonicalPath(any) client is closed");
 	}
 
 	@SuppressWarnings("unused")