Parse error on reserved keyword in enumerations

[riz0id]

The proto3-suite parser does not know how to interpret uses of the reserved keyword inside of enum statements. For example, the following protocol buffer:

syntax = "proto3";
package TestReservedEnum;

enum ReservedEnum {
  reserved 1, 2 to 8;
  UNSPECIFIED = 0;
}

will produce the following error when given as input to the compile-proto-file executable:

CompileParseError "/Users/jacob.leach/Documents/Haskell/proto3-suite/enum_test.proto" (line 7, column 12):
unexpected "1"
expecting "="

We should be able to parse reserved in enum statements according the proto2/proto3 "specification", see: https://protobuf.dev/programming-guides/proto3/#reserved.

[riz0id]

@j6carey notes that it would be nice if a code generation error was issued whenever a reserved name or field number is used for something else.