[CodeCompletion] Parse multiple catch clauses if the do body contains the code completion token

[ahoppen]

• Explanation: If a do statement’s body contained a code completion token, we would only parse a single catch clause for it, which would leave the second catch clause to be parsed as a standalone pattern without an initializer. Such a standalone pattern can cause type checking of closures to fail, resulting in no code completion results inside the do body.
• Scope: Parsing of do statements with a code completion token in the do body and multiple catch clauses
• Risk: Low, only affects code completion
• Testing: Added test case
• Issue: rdar://125303959
• Reviewer: @rintaro and @hamishknight on [CodeCompletion] Parse multiple catch clauses if the do body contains the code completion token #72910

[ahoppen]

@swift-ci Please test