Treat response.text() as a promise in error handling. (#11)

We [recently added some better exception handling](#9) but unfortunately printing the response body isn't working because [`response.text()` is a Promise](https://github.github.io/fetch/#response-body). The message looks like this: `ThriftRequestError: Thrift request failed: HTTP 503 Service Unavailable: [object Promise]`

The fix is to use `.then()` to get the body.

I have not tested this. I did run `npm run test` and some of the tests pass, but 75 out of 108 thrift-integration tests fail. I'm seeing this error a lot:
```
request to http://localhost:8090/thrift failed, reason: connect ECONNREFUSED ::1:8090
```
I think it also might have been happening before this change. It looks unrelated. It seems like it's happening because [Hapi listens on 127.0.0.1](https://hapi.dev/api/?v=20.2.2#-serveroptionsaddress) and [Node v17 and higher stopped forcing IPv64addresses to be listed first when resolving domains](nodejs/node#40537 (comment)) so now IPv6 addresses can be returned first. I'll probably post a separate PR for that, but for now I'd prefer not to block this change.

packages/thrift-client/src/main/connections/HttpConnection.ts

@@ -207,14 +207,20 @@ export class HttpConnection extends ThriftConnection<RequestOptions> {
           if (shouldRetry(response, retry, this.withEndpointPerMethod)) {
             resolve(this.write(dataToWrite, methodName, options, true))
           } else if (isErrorResponse(response)) {
-            reject(
-              new ThriftRequestError(
-                `Thrift request failed: HTTP ${response.status} ${
-                  response.statusText
-                }: ${response.text()}`,
-                response
+            const baseMessage = `Thrift request failed: HTTP ${response.status} ${response.statusText}`
+            response
+              .text()
+              .then(responseText =>
+                reject(new ThriftRequestError(`${baseMessage}: ${responseText}`, response))
               )
-            )
+              .catch(reason => {
+                reject(
+                  new ThriftRequestError(
+                    `${baseMessage} and the response body could not be read: ${reason}`,
+                    response
+                  )
+                )
+              })
           } else {
             response.arrayBuffer().then(arrayBuffer =>
               resolve({