This commit teaches parser to generate code block syntax node. As a support for this,
SyntaxParsingContext can be created by a single syntax kind, indicating the whole context
should be parsed into a node of that given syntax. Another change is to bridge created syntax
node with the given context kind. For instance, if a statement context results into an expression
node, the expression node will be bridged to a statement by wrapping it with a ExpressionStmt
node.
* Re-apply "libSyntax: Ensure round-trip printing when we build syntax tree from parser incrementally. (#12709)"
* Re-apply "libSyntax: Root parsing context should hold a reference to the current token in the parser, NFC."
* Re-apply "libSyntax: avoid copying token text when lexing token syntax nodes, NFC. (#12723)"
* Actually fix the container-overflow issue.
