Allow referencing existing resources with the 'existing' keyword

[anthony-c-martin]

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Adds the ability to reference runtime properties from an existing resource which is not being deployed by the Bicep file.

Fixes #258

[miqm]

I think more "natural" syntax would be existing resource res 'Provider/Type@version' = { } or even just existing res 'Provider/Type@version' = { } (without resource keyword)

[anthony-c-martin]

I think more "natural" syntax would be existing resource res 'Provider/Type@version' = { } or even just existing res 'Provider/Type@version' = { } (without resource keyword)

Please comment on #258 for syntax discussion - this PR is just to implement the design we closed on. I do think there's scope for changing this and definitely share some of your thoughts here, but it'll have to come in as a later revision.

[codecov-io]

Codecov Report

Merging #1339 (5fd94b5) into main (37a4cce) will decrease coverage by 0.07%.
The diff coverage is 92.53%.

@@            Coverage Diff             @@
##             main    #1339      +/-   ##
==========================================
- Coverage   94.80%   94.73%   -0.08%     
==========================================
  Files         351      352       +1     
  Lines       18348    18494     +146     
  Branches       14       14              
==========================================
+ Hits        17395    17520     +125     
- Misses        953      974      +21     

Flag	Coverage Δ
dotnet	95.23% <92.53%> (-0.08%)	⬇️
typescript	27.20% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...Core.IntegrationTests/Emit/TemplateEmitterTests.cs	100.00% <ø> (ø)
...cep.Core/TypeSystem/Az/ManagementGroupScopeType.cs	80.00% <0.00%> (-20.00%)	⬇️
...Bicep.Core/TypeSystem/Az/ResourceGroupScopeType.cs	80.00% <0.00%> (-20.00%)	⬇️
.../Bicep.Core/TypeSystem/Az/SubscriptionScopeType.cs	80.00% <0.00%> (-20.00%)	⬇️
src/Bicep.Core/TypeSystem/Az/TenantScopeType.cs	60.00% <0.00%> (-20.00%)	⬇️
src/Bicep.LangServer/SemanticTokenVisitor.cs	0.00% <0.00%> (ø)
src/Bicep.Core/Syntax/SyntaxRewriteVisitor.cs	71.42% <40.00%> (+0.11%)	⬆️
src/Bicep.Core/TypeSystem/ResourceScopeType.cs	60.00% <50.00%> (ø)
src/Bicep.Core/TypeSystem/ModuleType.cs	87.50% <66.66%> (-12.50%)	⬇️
src/Bicep.Core/TypeSystem/ResourceType.cs	90.00% <66.66%> (-10.00%)	⬇️
... and 39 more

[alex-frankel]

Thanks for adding the doc update. I can update https://github.com/Azure/bicep/blob/main/docs/arm2bicep.md when this gets checked in

[majastrz]

[shenglol]

Looks great!