[api-major] Replace MissingPDFException and UnexpectedResponseException with one exception

These old exceptions have a fair amount of overlap given how/where they are being used, which is likely because they were introduced at different points in time, hence we can shorten and simplify the code by replacing them with a more general `ResponseException` instead.

Besides an error message, the new `ResponseException` instances also include:
 - A numeric `status` field containing the server response status, similar to the old `UnexpectedResponseException`.

 - A boolean `missing` field, to allow easily detecting the situations where `MissingPDFException` was previously thrown.

web/app.js

@@ -50,12 +50,11 @@ import {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  MissingPDFException,
   PDFWorker,
+  ResponseException,
   shadow,
   stopEvent,
   TouchManager,
-  UnexpectedResponseException,
   version,
 } from "pdfjs-lib";
 import { AppOptions, OptionKind } from "./app_options.js";
@@ -1108,10 +1107,10 @@ const PDFViewerApplication = {
         let key = "pdfjs-loading-error";
         if (reason instanceof InvalidPDFException) {
           key = "pdfjs-invalid-file-error";
-        } else if (reason instanceof MissingPDFException) {
-          key = "pdfjs-missing-file-error";
-        } else if (reason instanceof UnexpectedResponseException) {
-          key = "pdfjs-unexpected-response-error";
+        } else if (reason instanceof ResponseException) {
+          key = reason.missing
+            ? "pdfjs-missing-file-error"
+            : "pdfjs-unexpected-response-error";
         }
         return this._documentError(key, { message: reason.message }).then(
           () => {

web/app_options.js

@@ -442,6 +442,7 @@ const defaultOptions = {
           : "../web/wasm/",
     kind: OptionKind.API,
   },
+
   workerPort: {
     /** @type {Object} */
     value: null,

web/pdfjs.js

@@ -37,7 +37,6 @@ const {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  MissingPDFException,
   noContextMenu,
   normalizeUnicode,
   OPS,
@@ -49,12 +48,12 @@ const {
   PermissionFlag,
   PixelsPerInch,
   RenderingCancelledException,
+  ResponseException,
   setLayerDimensions,
   shadow,
   stopEvent,
   TextLayer,
   TouchManager,
-  UnexpectedResponseException,
   Util,
   VerbosityLevel,
   version,
@@ -85,7 +84,6 @@ export {
   InvalidPDFException,
   isDataScheme,
   isPdfFile,
-  MissingPDFException,
   noContextMenu,
   normalizeUnicode,
   OPS,
@@ -97,12 +95,12 @@ export {
   PermissionFlag,
   PixelsPerInch,
   RenderingCancelledException,
+  ResponseException,
   setLayerDimensions,
   shadow,
   stopEvent,
   TextLayer,
   TouchManager,
-  UnexpectedResponseException,
   Util,
   VerbosityLevel,
   version,