Closes #453

Generate cocreatable types as classes with `[ComImport]`

Check whether Span<T> exists before using it

We were only promoting members in templates whose declaring types explicitly specified a visibility modifier.
Fixes #457

Promote visibility of members in all templates

This reverts commit 4c14435.

Roslyn doesn't let us provide our own binding redirects, so we have to take this ugly hack in order to consolidate versions or consume newer assemblies than what may ship with the compiler.

Re-apply System.Text.Encodings.Web update

Bumps [Microsoft.SourceLink.GitHub](https://github.com/dotnet/sourcelink) from 1.0.0 to 1.1.1.
- [Release notes](https://github.com/dotnet/sourcelink/releases)
- [Commits](dotnet/sourcelink@1.0.0...1.1.1)

---
updated-dependencies:
- dependency-name: Microsoft.SourceLink.GitHub
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Bumps [Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit](https://github.com/dotnet/roslyn-sdk) from 1.1.1-beta1.21480.3 to 1.1.1-beta1.21555.1.
- [Release notes](https://github.com/dotnet/roslyn-sdk/releases)
- [Commits](https://github.com/dotnet/roslyn-sdk/commits)

---
updated-dependencies:
- dependency-name: Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Bumps [Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit](https://github.com/dotnet/roslyn-sdk) from 1.1.1-beta1.21555.1 to 1.1.1-beta1.21615.2.
- [Release notes](https://github.com/dotnet/roslyn-sdk/releases)
- [Commits](https://github.com/dotnet/roslyn-sdk/commits)

---
updated-dependencies:
- dependency-name: Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Update metadata to 17.0.2-preview

* Update the name of the signing service connection

* Need to update another .yml