[bug](s3) fix S3 file system gets absolute path (#44965)

### What problem does this PR solve?

Issue Number: close #44902

Related PR: #xxx

###  Problem Summary
If we create a S3 resource for cooldown data storage and the
s3.root.path has a leading slash(/), such as: /root, the remote S3 data
file will not be deleted if we drop the cooldown tablet from Doris.

### Reason
Doris will get the path of all files of a tablet and then delete those
files, The AWS `S3Client:ListObjectsV2` uses objects prefix to get the
object files, but if the prefix has a leading slash(/),
the`S3Client:ListObjectsV2` gets empty result.

### Solution
use _prefix instead of _root_path in S3FileSystem for getting absolute
path, _prefix is normalized in constructor and it is removed the first
and last '/'.

### test case
1. create a s3 resource with a leading '/' and a storage policy base on
it:
```
CREATE RESOURCE "test_resource"
PROPERTIES
(
    "type" = "s3",
    "s3.endpoint" = "xxx",
    "s3.region" = "xxx",
    "s3.bucket" = "xxx",
    "s3.root.path" = "/tmp",
    "s3.access_key" = "xx",
    "s3.secret_key" = "xx"
);

CREATE STORAGE POLICY test_policy PROPERTIES (
    "storage_resource" = "test_resource",
    "cooldown_ttl" = "1"
)
```
2. create a table and set the storage_policy to `test_policy` and insert
test data:
```
CREATE TABLE `test_table` (
  `k` bigint,
  `v` bigint
) ENGINE=OLAP
DUPLICATE KEY(`k`)
DISTRIBUTED BY HASH(`k`) BUCKETS 1
PROPERTIES (
"replication_num" = "1",
"storage_policy" = "test_policy"
);

insert into test_table values (1,2),(2,3);
```
3. wait for the rowset cooldown to s3.
4. truncate test table
```
truncate table test_table force;
```
5. If we get a log like ` delete remote rowsets of tablet.
root_path="/tmp", tablet_id=xxx` in be.INFO, the remote tablet file
should be deleted.

### Release note

None

### Check List (For Author)

- Test <!-- At least one of them must be included. -->
    - [x] Regression test
    - [x] Unit Test
    - [x] Manual test (add detailed scripts or steps below)
    - [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
        - [ ] Previous test can cover this change.
        - [ ] No code files have been changed.
        - [ ] Other reason <!-- Add your reason?  -->

- Behavior changed:
    - [x] No.
    - [ ] Yes. <!-- Explain the behavior change -->

- Does this need documentation?
    - [x] No.
- [ ] Yes. <!-- Add document PR link here. eg:
apache/doris-website#1214 -->

### Check List (For Reviewer who merge this PR)

- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR
should merge into -->

Author: DarvenDuan

be/src/io/fs/s3_file_system.h

@@ -121,7 +121,7 @@ class S3FileSystem final : public RemoteFileSystem {
             abs_path = path;
         } else {
             // path with no schema
-            abs_path = _root_path / path;
+            abs_path = _prefix / path;
         }
         return Status::OK();
     }