Meta: Requirements use by pkg/angular_analyzer

[matanlurey]

• Support parsing expressions without throwing when a failure occurs
• Include offset data in parseExpression
• Add visitExpression to TemplateAstVisitor
• Add support for accept to BananaAst and StarAst for tooling teams
• Check trailing expressions (see implementation)
• TemplateAstVisitor#visit should delegate to TemplateAst#accept.