refactor(instrumentation-xhr): fix eslint warnings

```
/home/runner/work/opentelemetry-js/opentelemetry-js/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts
  66:28  warning  Don't use `Function` as a type  @typescript-eslint/ban-types

/home/runner/work/opentelemetry-js/opentelemetry-js/experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts
  44:16  warning  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any
  45:21  warning  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any

/home/runner/work/opentelemetry-js/opentelemetry-js/experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts
  69:22  warning  Don't use `Function` as a type  @typescript-eslint/ban-types
  104:22  warning  Don't use `Function` as a type  @typescript-eslint/ban-types
```

The middle ones are the same as #5401, the rest are replacing
`Function` with a more specific call signature, and they are either
in tests or private API, so no breakages expected.

Ref #5365

experimental/packages/opentelemetry-instrumentation-xml-http-request/src/types.ts

@@ -63,7 +63,7 @@ export interface XhrMem {
     entries: PerformanceResourceTiming[];
   };
   // callback to remove events from xhr once the span ends
-  callbackToRemoveEvents?: Function;
+  callbackToRemoveEvents?: () => void;
 }
 
 export type PropagateTraceHeaderCorsUrl = string | RegExp;

experimental/packages/opentelemetry-instrumentation-xml-http-request/src/utils.ts

@@ -24,6 +24,10 @@ const DIAG_LOGGER = api.diag.createComponentLogger({
     '@opentelemetry/opentelemetry-instrumentation-xml-http-request/utils',
 });
 
+function isDocument(value: unknown): value is Document {
+  return typeof Document !== 'undefined' && value instanceof Document;
+}
+
 /**
  * Helper function to determine payload content length for XHR requests
  * @param body
@@ -32,17 +36,17 @@ const DIAG_LOGGER = api.diag.createComponentLogger({
 export function getXHRBodyLength(
   body: Document | XMLHttpRequestBodyInit
 ): number | undefined {
-  if (typeof Document !== 'undefined' && body instanceof Document) {
+  if (isDocument(body)) {
     return new XMLSerializer().serializeToString(document).length;
   }
+
   // XMLHttpRequestBodyInit expands to the following:
-  if (body instanceof Blob) {
-    return body.size;
+  if (typeof body === 'string') {
+    return getByteLength(body);
   }
 
-  // ArrayBuffer | ArrayBufferView
-  if ((body as any).byteLength !== undefined) {
-    return (body as any).byteLength as number;
+  if (body instanceof Blob) {
+    return body.size;
   }
 
   if (body instanceof FormData) {
@@ -53,8 +57,9 @@ export function getXHRBodyLength(
     return getByteLength(body.toString());
   }
 
-  if (typeof body === 'string') {
-    return getByteLength(body);
+  // ArrayBuffer | ArrayBufferView
+  if (body.byteLength !== undefined) {
+    return body.byteLength;
   }
 
   DIAG_LOGGER.warn('unknown body type');

experimental/packages/opentelemetry-instrumentation-xml-http-request/test/xhr.test.ts

@@ -66,7 +66,7 @@ const XHR_TIMEOUT = 2000;
 const getData = (
   req: XMLHttpRequest,
   url: string,
-  callbackAfterSend: Function,
+  callbackAfterSend: () => void,
   async?: boolean
 ) => {
   // eslint-disable-next-line no-async-promise-executor
@@ -101,7 +101,7 @@ const postData = (
   req: XMLHttpRequest,
   url: string,
   data: Document | XMLHttpRequestBodyInit,
-  callbackAfterSend: Function,
+  callbackAfterSend: () => void,
   async?: boolean
 ) => {
   // eslint-disable-next-line no-async-promise-executor