compiler: handle grammar-sensitive suites and calls

[floitsch]

Part 7 of 10 in the AST-driven Toit pretty-printer stack. Depends on #3191.

Summary

• format suite-bearing calls and declarations in conditions
• preserve nested call argument structure
• keep semantic separation around comments
• parenthesize binary, conditional, nested-call, prefix-not, and grouped-suite arguments when required by Toit grammar
• format suites in statement contexts
• use leading broken binary operators, except trailing and/or

Verification

• focused public-command gold cases cover blocks, lambdas, named suites, nested calls, condition declarations, and grammar-sensitive arguments
• every formatted result is reparsed and checked for AST equivalence

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