Add new SQL parser to support S3 Select syntax (#7102)

- New parser written from scratch, allows easier and complete parsing
  of the full S3 Select SQL syntax. Parser definition is directly
  provided by the AST defined for the SQL grammar.

- Bring support to parse and interpret SQL involving JSON path
  expressions; evaluation of JSON path expressions will be
  subsequently added.

- Bring automatic type inference and conversion for untyped
  values (e.g. CSV data).

vendor/github.com/alecthomas/participle/doc.go

@@ -0,0 +1,73 @@
+// Package participle constructs parsers from definitions in struct tags and parses directly into
+// those structs. The approach is philosophically similar to how other marshallers work in Go,
+// "unmarshalling" an instance of a grammar into a struct.
+//
+// The supported annotation syntax is:
+//
+//		- `@<expr>` Capture expression into the field.
+//		- `@@` Recursively capture using the fields own type.
+//		- `<identifier>` Match named lexer token.
+//		- `( ... )` Group.
+//		- `"..."` Match the literal (note that the lexer must emit tokens matching this literal exactly).
+//		- `"...":<identifier>` Match the literal, specifying the exact lexer token type to match.
+//		- `<expr> <expr> ...` Match expressions.
+//		- `<expr> | <expr>` Match one of the alternatives.
+//
+// The following modifiers can be used after any expression:
+//
+//		- `*` Expression can match zero or more times.
+//		- `+` Expression must match one or more times.
+//		- `?` Expression can match zero or once.
+//		- `!` Require a non-empty match (this is useful with a sequence of optional matches eg. `("a"? "b"? "c"?)!`).
+//
+// Supported but deprecated:
+//
+//		- `{ ... }` Match 0 or more times (**DEPRECATED** - prefer `( ... )*`).
+//		- `[ ... ]` Optional (**DEPRECATED** - prefer `( ... )?`).
+//
+// Here's an example of an EBNF grammar.
+//
+//     type Group struct {
+//         Expression *Expression `"(" @@ ")"`
+//     }
+//
+//     type Option struct {
+//         Expression *Expression `"[" @@ "]"`
+//     }
+//
+//     type Repetition struct {
+//         Expression *Expression `"{" @@ "}"`
+//     }
+//
+//     type Literal struct {
+//         Start string `@String` // lexer.Lexer token "String"
+//         End   string `("…" @String)?`
+//     }
+//
+//     type Term struct {
+//         Name       string      `  @Ident`
+//         Literal    *Literal    `| @@`
+//         Group      *Group      `| @@`
+//         Option     *Option     `| @@`
+//         Repetition *Repetition `| @@`
+//     }
+//
+//     type Sequence struct {
+//         Terms []*Term `@@+`
+//     }
+//
+//     type Expression struct {
+//         Alternatives []*Sequence `@@ ("|" @@)*`
+//     }
+//
+//     type Expressions []*Expression
+//
+//     type Production struct {
+//         Name        string      `@Ident "="`
+//         Expressions Expressions `@@+ "."`
+//     }
+//
+//     type EBNF struct {
+//         Productions []*Production `@@*`
+//     }
+package participle