misuse of metabuild.NewContext() when create TableInfo

[lance6716]

https://github.com/search?q=repo%3Apingcap%2Ftiflow%20BuildTableInfoFromAST(metabuild.NewContext()%2C%20stmt)&type=code

The default metabuild.NewContext() has strict SQL mode flags, it will reject some SQL like default zero datetime.

Should use NewNonStrictContext() instead

[lance6716]

/cc @D3Hunter @3AceShowHand