fix: use empty string as the default label and check autolabel statements

[wodeni]

Description

Related issue/PR: #752

When NoLabel is used or no labeling statements exist for a Substance variable, the current system doesn't insert a label field for that variable in the Translation. This often causes expected errors. In this PR, we change the default to empty strings as default labels even when there's no labeling statements.

Implementation strategy and design decisions

• AutoLabel None should define an empty label #752 also uncovers a bug in the Substance checker: we didn't check the variables of statements like AutoLabel A, B, C. Added the checking in the Substance checker.
• Changed Substance postprocessing to insert default "" labels for every variable and insert "" for NoLabel statements

Examples with steps to reproduce them

[codecov]

Codecov Report

Merging #754 (4141aa5) into main (df8d0aa) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #754      +/-   ##
==========================================
+ Coverage   65.60%   65.61%   +0.01%     
==========================================
  Files          46       46              
  Lines        8144     8147       +3     
  Branches     1525     1525              
==========================================
+ Hits         5343     5346       +3     
  Misses       2792     2792              
  Partials        9        9              

Impacted Files	Coverage Δ
packages/core/src/compiler/Style.ts	87.50% <100.00%> (-0.02%)	⬇️
packages/core/src/compiler/Substance.ts	91.17% <100.00%> (+0.13%)	⬆️

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[keenancrane]

Awesome! Looks good. Thank you @wodeni!

[keenancrane]

@wodeni Does AutoLabel None no longer work as of this PR? When I add

AutoLabel None

To my Substance program I get

Variable None (at line 12, column 11 of Substance program) does not exist.

Seems it's checking to see if None is a variable name. But shouldn't the only things following AutoLabel be either All or None? (And we only need to check for a variable name after Label, not AutoLabel?)

[wodeni]

@wodeni Does Autolabel None no longer work as of this PR? I get

Variable None (at line 12, column 11 of Substance program) does not exist.

Autolabel None is never supported iirc.