[improve] Supports http request use utf8 charset

[gnehil]

Proposed changes

Issue Number: close #xxx

Problem Summary:

When writing column names containing Chinese or other Unicode characters, stream load will return the following exception information：

{
    "TxnId": 2060,
    "Label": "doris-0-0-0-1763547930966",
    "Comment": "",
    "TwoPhaseCommit": "false",
    "Status": "Fail",
    "Message": "[ANALYSIS_ERROR]TStatus: errCode = 2, detailMessage = Duplicate column: ??",
    "NumberTotalRows": 0,
    "NumberLoadedRows": 0,
    "NumberFilteredRows": 0,
    "NumberUnselectedRows": 0,
    "LoadBytes": 0,
    "LoadTimeMs": 0,
    "BeginTxnTimeMs": 0,
    "StreamLoadPutTimeMs": 1,
    "ReadDataTimeMs": 0,
    "WriteDataTimeMs": 0,
    "ReceiveDataTimeMs": 0,
    "CommitAndPublishTimeMs": 0
}

You can now set sink.http-utf8-charset to true to configure the HTTP client to use the UTF-8 character set, allowing Unicode characters to be included in the header.

Checklist(Required)

1. Does it affect the original behavior: (Yes/No/I Don't know)
2. Has unit tests been added: (Yes/No/No Need)
3. Has document been added or modified: (Yes/No/No Need)
4. Does it need to update dependencies: (Yes/No)
5. Are there any changes that cannot be rolled back: (Yes/No)

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[JNSimba]

LGTM