branch-2.1:[fix](function)fix month=0 of from_iso8601_date function. (#53050)

[hubgeter]

bp #53050
Related PR: #40695
Problem Summary:

pr #40695 introduced the function from_iso8601_date, which parses the string to get year、mouth、 day, and sets the date value through the set_time_unit function.
Since set_time_unit lacks some judgment on mouth, it may get an illegal date in the end, which may cause core in debug mode.

sql : select from_iso8601_date('2023-00-01');

F20250709 09:50:14.366984 3587796 vdatetime_value.h:1222] Check failed: date_v2_value_.month_ != 0
*** Check failure stack trace: ***
    @     0x559bd7050d96  google::LogMessage::SendToLog()
    @     0x559bd704d7e0  google::LogMessage::Flush()
    @     0x559bd70515d9  google::LogMessageFatal::~LogMessageFatal()
    @     0x559bc725a570  doris::DateV2Value<>::set_time_unit<>()
    @     0x559bc7257380  doris::vectorized::FromIso8601DateV2::execute()
    @     0x559bc7255a88  doris::vectorized::FunctionOtherTypesToDateType<>::execute_impl()
    @     0x559bc09e0781  doris::vectorized::DefaultExecutable::execute_impl()
    @     0x559bc423aa20  doris::vectorized::PreparedFunctionImpl::_execute_skipped_constant_deal()
    @     0x559bc4234938  doris::vectorized::PreparedFunctionImpl::execute_without_low_cardinality_columns()
    @     0x559bc4233f42  doris::vectorized::PreparedFunctionImpl::default_implementation_for_nulls()
    @     0x559bc423a773  doris::vectorized::PreparedFunctionImpl::_execute_skipped_constant_deal()
    @     0x559bc4234938  doris::vectorized::PreparedFunctionImpl::execute_without_low_cardinality_columns()
    @     0x559bc4234a57  doris::vectorized::PreparedFunctionImpl::execute()

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • 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

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hubgeter]

run buildall

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[doris-robot]

BE UT Coverage Report

Increment line coverage 100.00% (6/6) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	39.09% (10349/26473)
Line Coverage	30.10% (86049/285836)
Region Coverage	28.81% (44460/154308)
Branch Coverage	25.52% (22754/89154)