Support import true or false as boolean value

[yangzhg]

Fixes #3831
After this PR
insert into: 1/"1" -> 1, 0/"0"->0, true/"true"->1, false/"false" -> 0, "10"->null, "xxxx" -> null
load: 1/true -> 1, 0/false -> 0, other -> null

[caiconghui]

@yangzhg Hi, I think the result of processing bool value for stream load and insert stmt should keep consistent.
For now, like insert into xx values(1), result=true, insert into xx values(0) result=false, insert into xxx values("false") result=true insert into xx values(false) result=false insert into xx values("0") result=true, insert into xx values(true) result=true.
This is because insert stmt can analyze the real data type for insert value, so like 1 2 3, will use int_cast_to_bool, even can analyze boolean type. but for stream load, we lost the data type information. we don't know the real data type of the value, we treat all column values as string, so I think may be stream load should be processed specially to keep consistent with insert stmt. maybe need more discussion.

[yangzhg]

@yangzhg Hi, I think the result of processing bool value for stream load and insert stmt should keep consistent.
For now, like insert into xx values(1), result=true, insert into xx values(0) result=false, insert into xxx values("false") result=true insert into xx values(false) result=false insert into xx values("0") result=true, insert into xx values(true) result=true.
This is because insert stmt can analyze the real data type for insert value, so like 1 2 3, will use int_cast_to_bool, even can analyze boolean type. but for stream load, we lost the data type information. we don't know the real data type of the value, we treat all column values as string, so I think may be stream load should be processed specially to keep consistent with insert stmt. maybe need more discussion.

@chaoyli Insert into xx values("0") and stream load import file 0 is not consistent in the current code. Insert into xx values("0") result=true, stream load 0 result=false, and now cast_to_bool Only occurs when the type of the column is bool, so it is not contradictory to the current insert

[chaoyli]

I think the meaning of caiconghui is to make consistent of stream load and insert in any situation.
Otherwise, it will cause some misunderstanding. @yangzhg

[yangzhg]

@yangzhg Hi, I think the result of processing bool value for stream load and insert stmt should keep consistent.
For now, like insert into xx values(1), result=true, insert into xx values(0) result=false, insert into xxx values("false") result=true insert into xx values(false) result=false insert into xx values("0") result=true, insert into xx values(true) result=true.
This is because insert stmt can analyze the real data type for insert value, so like 1 2 3, will use int_cast_to_bool, even can analyze boolean type. but for stream load, we lost the data type information. we don't know the real data type of the value, we treat all column values as string, so I think may be stream load should be processed specially to keep consistent with insert stmt. maybe need more discussion.

@caiconghui I will change the insert statement and stream load to keep consistent with mysql