[SwiftLexicalLookup][GSoC] New lookup method signature and `Identifier` initializer changes#2789

DougGregor merged 4 commits intoswiftlang:mainswiftlang/swift-syntax:mainfrom

MAJKFL:guard-sequential-suggeested-changesMAJKFL/swift-syntax:guard-sequential-suggeested-changesCopy head branch name to clipboard