Generate Holder struct in espr

[termoshtt]

Another approach of #45 for #13

TODO

• Holder struct
• impl Holder for each Holder -> Holder for Box<dyn XxxAny> #57
• Tables
• impl EntityTable for Tables
• Tables::from_section -> After serde integration for ENUMERATION and SELECT #41 with test
• Tables::xxx_iter

[termoshtt]

PlaceHolder requires Clone, which has been dropped in #51.

[termoshtt]

For impl Holder we have to check a TypeRef is SimpleType or not, but it is not possible currently due to reference case.

TYPE a = INTEGER; ENDTYPE;
TYPE b = a; ENDTYPE;

In this example, the UnderlyingType of a is UnderlyingType::Simple, and thus we can distinguish it is primitive type. Howerver, it for b is UnderlyingType::Referece, which can be both Simple or not. We have to distinguish in IR level rather than Rust code generation level.

[termoshtt]

error[E0599]: the method `into_owned` exists for enum `tables::PlaceHolder<Direction>`, but its trait bounds were not satisfied
    --> ruststep/src/ap201.rs:8613:42
     |
5014 |     pub struct Direction {
     |     --------------------
     |     |
     |     doesn't satisfy `<Direction as tables::Holder>::Owned = _`
     |     doesn't satisfy `Direction: tables::Holder`
...
8613 |                 orientation: orientation.into_owned(tables)?,
     |                                          ^^^^^^^^^^ method cannot be called on `tables::PlaceHolder<Direction>` due to unsatisfied trait bounds
     | 
    ::: ruststep/src/tables.rs:93:1
     |
93   | pub enum PlaceHolder<T> {
     | ----------------------- method `into_owned` not found for this
     |
     = note: the following trait bounds were not satisfied:
             `Direction: tables::Holder`
             `<Direction as tables::Holder>::Owned = _`

still has critical problem. Should split it from this PR