Refactor Module

[HoshinoTented]

This PR redesigned the module system:

• import data::nat can be referred by nat rather than data::nat
• ambiguous on exported symbol is not allowed, therefore we don't need to solve ambiguity when importing , so UseHide.Name should store a single string rather than QualifiedID
• better candidate implementation (a dedicated class rather than a list/map)

[ice1000]

Do you intend to supersede ModuleExport with ModuleExport2? (and also the other similarly named classes)

[HoshinoTented]

Do you intend to supersede ModuleExport with ModuleExport2? (and also the other similarly named classes)

Yes, I keep it because I am too lazy to delete it.

[HoshinoTented]

The code compiles. However, there are some problems: We have a lot of usage of import xxx::base, and they cause name conflicts since the name base.

[HoshinoTented]

Well, a lot of code is reverted cause:

• We need ModuleName.Qualified as the name of module (see last comment)
• I was trying to keep the tree structure of modules, but I found that we can rebuild it from flattened module names, except we lost the layer information (we can not tell whether a module is directly or indirectly importing, but ResolveInfo can tell)

[HoshinoTented]

However, I found an unnatural place in CompiledModule::SerExport, and I fixed it in this PR.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.16832% with 34 lines in your changes missing coverage. Please review.

Project coverage is 79.77%. Comparing base (8f52aab) to head (5bbf969). Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
...ain/java/org/aya/resolve/context/ModuleExport.java	70.73%	4 Missing and 8 partials :warning:
...in/java/org/aya/resolve/context/ModuleContext.java	78.37%	4 Missing and 4 partials :warning:
...main/java/org/aya/cli/interactive/ReplContext.java	91.22%	0 Missing and 5 partials :warning:
...ain/java/org/aya/resolve/context/ModuleSymbol.java	55.55%	4 Missing :warning:
...c/main/java/org/aya/resolve/context/Candidate.java	88.00%	2 Missing and 1 partial :warning:
...c/main/java/org/aya/resolve/error/NameProblem.java	50.00%	1 Missing :warning:
.../java/org/aya/resolve/visitor/StmtPreResolver.java	75.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1135 +/- ## ============================================ + Coverage 79.44% 79.77% +0.33% + Complexity 3361 3356 -5 ============================================ Files 306 307 +1 Lines 10172 10158 -14 Branches 1228 1220 -8 ============================================ + Hits 8081 8104 +23 + Misses 1411 1388 -23 + Partials 680 666 -14 ```

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[ice1000]

bors r+