This will add helpers to get the underlying raw entities or constructor
arguments on stubs for synthesized classes.
For example a schema like:
```
@synth.from_class(A)
class B:
pass
@synth.on_arguments(base=A, index=int)
class C:
pass
```
will generate
```
cached
private Raw::A getUnderlyingEntity() { this = Synth::TB(result) }
```
in the `B.qll` stub and
```
cached
private Raw::A getUnderlyingBase() { this = Synth::TC(result, _) }
cached
private int getUnderlyingIndex() { this = Synth::TC(_, result) }
```
in the `C.qll` stub.
As stubs these can be freely changed later on.
In those kinds of tests the results may have different final classes
that are not necessarily visible (or tested) solely through the string
representation. For better testing and reading of expected results,
`getQlPrimaryClasses` is added in these cases.
There was an issue in case multiple inheritance from classes with
children was involved, where indexes would overlap.
The generated code structure has been reshuffled a bit, with
`Impl::getImmediateChildOf<Class>` predicates giving 0-based children
for a given class, including those coming from bases, and the final
`Impl::getImmediateChild` disjuncting the above on final classes only.
This removes the need of `getMaximumChildrenIndex<Class>`, and also
removes the code scanning alerts.
Also, comments were fixed addressing the review.
This replaces numeric tag-based prefixes with the actual tag name.
While this means in general slightly larger trap files, it aids
debugging them for a human.
In the future we can make this conditional on some kind of trap debug
option, but for the moment it does not seem detrimental.
This adds:
* a base `README.md` file to `codegen`
* module docstrings for the modules in `generators`
* help strings on all command line flags
Moreover some unneeded command line flags (`--namespace`,
`--include-dir` and `--trap-affix`) have been dropped.
