[summary]
when adapting from 5.7 to 8.0:
we made a mistake on `unit_for_union->item_list` to `unit_for_union->get_fields_list()`

[summary]
1. support alter table rename t1 t2
2. support alter add/drop primary key

in some cases, can insert same values by primary key after atler table add
primary key.

[summary]
1. add/fix mtr for alter table
2. support alter table: mix add/drop column、order column and other syntaxs to use

Cause:
result_output has not been prepare() in Engine::Execute
Solution:
add condition to allow union all sql run into prepare()
and exclude "create table as select" sql

[summary]
1. backport from 5.7
2. fix txn commit twice in CommitTx()
3. redefine int(0,1) to bool type.

Cause:
assert failed in function get_dpn().
When table is empty, it hasn't created a dpn and m_idx.size()=0.
Solution:
If m_idx.size()==0, return directly in (Un)lockPackFromUse function.

Cause:
The value of at_ has not be initialized in constructor of RCDateTime
So it cannot get correct datatype in RCDateTime::ToBString()
Solution:
Init at_ in constructor

[summary]
1. backport code
2. fix no txn version for table not commited by transaction.

[summary]
. The behaviour of delete ... where a is null in strict mode is
different with innodb, both in tianmu 5.7 & 8.0.

delete invalid workflows and update the `.gitignore` and Readme

[summary]
fix TPCH Q2/Q16/Q17/Q18/Q20/Q22
    Test results for reference:
    https://blog.csdn.net/adofsauron/article/details/127228984?spm=1001.2014.3001.5501

    TODO: Q4 and Q21
    The case is an exists subquery
    because the Tianmu engine converts
    the syntax tree to an inner join
    on an association surface.
    For details, see
    https://blog.csdn.net/adofsauron/article/details/127228984?spm=1001.2014.3001.5501

[summary]
1. fix assert failed in optimizer() funtion.
2. reorder code in AddJoins() to support left join with nested_joins.

feat(mtr): add issue669.test and enable some test cases & fix assert fail on optimizer caused by delete #1433

[summary]

The logic of this modification is as follows:

Descriptor object, MIUpdatingIterator object and DimensionVector are all newly defined objects this time. If you want iterators to work, you must have corresponding DimGroups. Because I didn't fully understand the usage of these classes, I used (dims. SetAll()) to set them, causing all DimGroups to converge.

The modification method is to use the corresponding virtual column to set DimGroups, so that the data volume is at most the data volume of the current table