fix issues found by Coverity Scan in texpr.c (branch: 2.6)

[xiaopingcs]

Bug Description
fix issues found by Coverity Scan in TDengine/src/common/src/texpr.c

To Reproduce
N/A

Expected Behavior
fix following issues:

Type	Category	Function	Line Number
Resource leak	Resource leaks	convertFilterSetFromBinary	1110
Untrusted allocation size	Insecure data handling	exprTreeFromBinaryImpl	977
Resource leak	Resource leaks	exprValidateTimeNode	Various
Self assignment	Incorrect expression	vectorTimeFunc	2936
Resource leak	Resource leaks	convertStringToTimestamp	2605
Resource leak	Resource leaks	exprTreeExprNodeTraverse	764
Resource leak	Resource leaks	exprTreeExprNodeTraverse	764

Screenshots
N/A

Environment (please complete the following information):
N/A

Additional Context
above issues found by https://scan.coverity.com/projects/tdengine?tab=overview