fix(sema): validate ternary conditions in return statements

[aryanbaranwal001]

This PR fixes two compiler panics caused by invalid ternary conditions used in return statements:

• Fixes Compiler panic in codegen: expr should not be in cfg: Poison when a void-returning call is used as a ternary condition #1865
• Fixes Compiler panic in codegen: List and Type Operator shall not appear in the CFG when type(T) is used as a ternary condition #1873

The root cause is that Solang has two sema paths for ternary expressions:

• The normal expression resolver handles generic ternaries at /sema/expression/resolve_expression.rs:180. It resolves the condition and validates it with cond.cast(...)? at /sema/expression/resolve_expression.rs:187.

• The return specific resolver handles ternaries inside return values at /sema/statements.rs:2034. It resolves the condition at line:2035, but did not apply the equivalent .cast(...) boolean check before storing the condition in Expression::ConditionalOperator.

Because of that missing check, invalid conditions such as type(bool) or a void returning function call slip through sema and reach codegen.

Fix

Add the missing boolean check .cast(...) after the condition is resolved at /sema/statements.rs:2042 and marked used at /sema/statements.rs:2043

used_variable(ns, &cond, symtable); // for reference

let cond = cond.cast(&cond.loc(), &Type::Bool, true, ns, diagnostics)?;

This makes sema reject invalid conditions like following before codegen:

• return type(bool) ? 1 : 2;
• return g() ? 1 : 2; where g() returns no value

This mirrors the existing generic ternary behavior at /sema/expression/resolve_expression.rs:187.