Serialize origin stmt in Rollup Job and MV Meta

[EmmyMiao87]

In materialized view 2.0, the define expr is serialized in column.
The method is that doris serialzie the origin stmt of Create Materialzied View Stmt in RollupJobV2 and MVMeta.
The define expr will be extract from the origin stmt after meta is deserialized.

The define expr is necessary for bitmap and hll materialized view.
For example:
MV meta: __doris_mv_bitmap_k1, bitmap_union, to_bitmap(k1)
Origin stmt: select bitmap_union(to_bitmap(k1)) from table
Deserialize meta: __doris_mv_bitmap_k1, bitmap_union, null
After extract: the define expr to_bitmap(k1) from origin stmt should be extracted.
__doris_mv_bitmap_v1, bitmap_union, to_bitmap(k1) (which comes from the origin stmt)

#3344

Change-Id: Ic2da093188d8985f5e97be5bd094e5d60d82c9a7

[HangyuanLiu]

The name defineStmt can easily cause ambiguity with DefineExpr. But this statement may not only parse the semantics of defineExpr in the future。MaterializedViewStmt is a better name ?

[EmmyMiao87]

The define stmt means that this is the definition of materialized views.

[HangyuanLiu]

LGTM

[imay]

LGTM