Match documentation extensions to symbols using link resolver

[d-ronnqvist]

Bug/issue #, if applicable:

• rdar://108392613 Documentation extension links can't use link resolution features #561
• rdar://76252171 Allow documentation extensions to omit module name when there's only one module #516
• rdar://108392639 DocC doesn't warn when a documentation file doesn't match a symbol  #560

Summary

This uses the link resolver to match documentation extensions with symbols. This allows for using link resolution features in documentation extension title links. For example:

• Documentation extension title links can now omit disambiguation when the colliding paths have different capitalization
• Documentation extension title links can now contain special characters
• Documentation extension title links can now omit the leading module name when the bundle only contains one module
• Documentation extension title links can now use Swift or Objective-C symbol names to extend the documentation for a symbol that's available in both languages
• Documentation extension title links that don't match any known symbol now result in a warning with the same rich information as other unresolved symbol links.

Dependencies

None

Testing

In a Swift package with a documentation catalog;

• Add code where two symbols have the same case insensitive name:

  public struct Outer {
      public enum Inner {}
      public var inner: Inner
  }
  

• Add a documentation extension file and link to one of the symbols without prefixing with the module and without disambiguation:

  # ``Outer/Inner``
  
  Some documentation extension content here.
  

  The content of this documentation extension file should be included on the documentation page for the Inner enumeration.

• Add another documentation extension file and link to a symbol that doesn't exist in the module:

  # ``ThisDoesNotExist``
  
  This should result in a warning
  

  There should be a warning saying that the module doesn't contain a "ThisDoesNotExist" symbol.

• Add another documentation extension file and link to first symbol but make the symbol link more spelled out:

  # ``MyModule/Outer/Inner-enum``
  
  This symbol already has a documentation extension elsewhere
  

  There should be a warning saying that multiple documentation extension files match the Inner enumeration.

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests
• Ran the ./bin/test script and it succeeded
• Updated documentation if necessary

[d-ronnqvist]

@swift-ci please test

[d-ronnqvist]

@swift-ci please test

[d-ronnqvist]

@swift-ci please test

[d-ronnqvist]

@swift-ci please test