Implement pretty-printing for union types

[shenglol]

Main changes:

• Updated the grammar and parser to allow an optional leading | as part of a union type expression.
• Improved the pretty-printing layout rule to handle union types surpassing the width limit. In such cases, a leading | will now be included to enhance readability. For instance:

// Before
type tupleUnion = ['foo', 'bar', 'baz'] | ['fizz', 'buzz'] | ['snap', 'crackle', 'pop']

// After
type tupleUnion =
  | ['foo', 'bar', 'baz']
  | ['fizz', 'buzz']
  | ['snap', 'crackle', 'pop']

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 7050176699)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 7050176699

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 7050176699"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 7050176699

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 7050176699"

[github-actions]

Test Results

     143 files  +     11       143 suites  +11   4h 12m 29s ⏱️ - 15m 59s
10 860 tests ±       0  10 859 ✔️  -        1  0 💤 ±0  1 ❌ +1 
55 223 runs  +2 860  55 222 ✔️ +2 859  0 💤 ±0  1 ❌ +1 

For more details on these failures, see this check.

Results for commit 0d681aa. ± Comparison against base commit 49b3002.

♻️ This comment has been updated with latest results.

[majastrz]