[tcgc] language's emitter should report tcgc's diagnostics

[tadelesh]

After emitter use TCGC createSdkContext, the returned SdkContext value contains all the diagnostics found when generating SDK interfaces in TCGC: diagnostics: readonly Diagnostic[];, language's emitter should report them when they use TCGC using the code: program.reportDiagnostics(sdkContext.diagnostics);

Current diagnostics in TCGC listed as follows:

"example-loading": {
  severity: "warning",
  messages: {
	default: paramMessage`Skipped loading invalid example file: ${"filename"}. Error: ${"error"}`,
	noDirectory: paramMessage`Skipping example loading from ${"directory"} because there was an error reading the directory.`,
	noOperationId: paramMessage`Skipping example file ${"filename"} because it does not contain an operationId and/or title.`,
  },
},
"duplicate-example-file": {
  severity: "error",
  messages: {
	default: paramMessage`Example file ${"filename"} uses duplicate title '${"title"}' for operationId '${"operationId"}'`,
  },
},
"example-value-no-mapping": {
  severity: "warning",
  messages: {
	default: paramMessage`Value in example file '${"relativePath"}' does not follow its definition:\n${"value"}`,
  },
},
"unexpected-http-param-type": {
  severity: "error",
  messages: {
	default: paramMessage`Expected parameter "${"paramName"}" to be of type "${"expectedType"}", but instead it is of type "${"actualType"}"`,
  },
},
"multiple-response-types": {
  severity: "warning",
  messages: {
	default: paramMessage`Multiple response types found in operation ${"operation"}. Only one response type is supported, so we will choose the first one ${"response"}`,
  },
},
"no-corresponding-method-param": {
  severity: "error",
  messages: {
	default: paramMessage`Missing "${"paramName"}" method parameter in method "${"methodName"}", when "${"paramName"}" must be sent to the service. Add a parameter named "${"paramName"}" to the method.`,
  },
},
"no-emitter-name": {
  severity: "warning",
  messages: {
	default: "Can not find name for your emitter, please check your emitter name.",
  },
},
"unsupported-generic-decorator-arg-type": {
  severity: "warning",
  messages: {
	default: paramMessage`Can not parse the arg type for decorator "${"decoratorName"}".`,
  },
},
"unsupported-protocol": {
  severity: "error",
  messages: {
	default: "Currently we only support HTTP and HTTPS protocols",
  },
},
"server-param-not-path": {
  severity: "error",
  messages: {
	default: paramMessage`Template argument ${"templateArgumentName"} is not a path parameter, it is a ${"templateArgumentType"}. It has to be a path.`,
  },
},
"multiple-services": {
  severity: "warning",
  messages: {
	default: paramMessage`Multiple services found in definition. Only one service is supported, so we will choose the first one ${"service"}`,
  },
},
"union-null": {
  severity: "error",
  messages: {
	default: "Cannot have a union containing only null types.",
  },
},
"discriminator-not-constant": {
  severity: "error",
  messages: {
	default: paramMessage`Discriminator ${"discriminator"} has to be constant`,
  },
},
"discriminator-not-string": {
  severity: "warning",
  messages: {
	default: paramMessage`Value of discriminator ${"discriminator"} has to be a string, not ${"discriminatorValue"}`,
  },
},
"unsupported-kind": {
  severity: "warning",
  messages: {
	default: paramMessage`Unsupported kind ${"kind"}`,
  },
},
"encoding-multipart-bytes": {
  severity: "error",
  messages: {
	default:
	  "Encoding should not be applied to bytes content in a multipart request. This is semi-incompatible with how multipart works in HTTP.",
  },
},
"conflict-usage-override": {
  severity: "warning",
  messages: {
	default: `@usage override conflicts with the usage calculated from operation or other @usage override.`,
  },
},
"conflict-access-override": {
  severity: "warning",
  messages: {
	default: `@access override conflicts with the access calculated from operation or other @access override.`,
  },
},
"conflicting-multipart-model-usage": {
  severity: "error",
  messages: {
	default: "Invalid encoding",
	wrongType: paramMessage`Model '${"modelName"}' cannot be used as both multipart/form-data input and regular body input. You can create a separate model with name 'model ${"modelName"}FormData' extends ${"modelName"} {}`,
  },
}

[weidongxu-microsoft]

blocked by #1510