[Bug](nereids) Fix UT when run test cases in package

[adonis0147]

Proposed changes

NamedExpressionUtil::clear should reset the nextId rather than create a new IdGenerator<ExprId> because the old one may be referenced by other objects and it may cause some cases start in a dirty environment when we run test cases in package.

Issue Number: close #12631

Problem summary

If we run the nereids test cases in package in Intellij IDEA, we will see some cases fail.

See #12631 .

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 (If Yes, please explain WHY)
   • 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...