metasheet: change container type from map to list

[wenchy]

Previously, we have talked deeply about:

• Proposal: support generating multiple messagers for the same sheet #328
• feat: support generating multiple messagers for the same sheet #332

Hoewever, if we change map<string, Metasheet> metasheet_map to repeated Metasheet sheet_list

tableau/proto/tableau/protobuf/internal/metabook.proto

Lines 12 to 16 in 8a16745

	message Metabook {
	option (tableau.worksheet) = {name:"@TABLEAU" namerow:1 datarow:2};
	map<string, Metasheet> metasheet_map = 1 [(tableau.field).key = "Sheet"];
	}

It has following benefits:

• Configure and generate multiple messages for the same sheet in the same metasheet
• More stable (controlled by game developers) and ordered generated messages by the metasheet list container but not native sheet order (controlled by game designers) in workbook

But it will introduce following breaking changes:

After prototyping, it will break the XML/YAML metatsheet forms which are currently unacceptable!

For yaml format example:

tableau/test/functest/testdata/default/yaml/metasheet/Merger.yaml

Lines 1 to 4 in dcdf1f8

	# define metasheet: generate all sheets
	"@sheet": "@TABLEAU"
	"YamlMergerConf":
	Merger: "Merger*.yaml"

will be changed to

# define metasheet: generate all sheets 
"@sheet": "@TABLEAU" 
"SheetList":
  - Name: "YamlMergerConf"
    Merger: "Merger*.yaml"