refactor: improve test isolation for Axios API logic (#13125)

* wip: commit progress on code split-up

* wip: commit more progress

* wip: finish initial version of class implementation

* chore: update all import paths to go through client instance

* fix: remove temp comments

* refactor: smoooooooosh the API

* refactor: update import setup for tests

site/src/contexts/ProxyContext.tsx

@@ -8,7 +8,7 @@ import {
   useState,
 } from "react";
 import { useQuery } from "react-query";
-import { getWorkspaceProxies, getWorkspaceProxyRegions } from "api/api";
+import { API } from "api/api";
 import { cachedQuery } from "api/queries/util";
 import type { Region, WorkspaceProxy } from "api/typesGenerated";
 import { useAuthenticated } from "contexts/auth/RequireAuth";
@@ -108,10 +108,11 @@ export const ProxyProvider: FC<PropsWithChildren> = ({ children }) => {
       metadata: metadata.regions,
       queryKey: ["get-proxies"],
       queryFn: async (): Promise<readonly Region[]> => {
-        const endpoint = permissions.editWorkspaceProxies
-          ? getWorkspaceProxies
-          : getWorkspaceProxyRegions;
-        const resp = await endpoint();
+        const apiCall = permissions.editWorkspaceProxies
+          ? API.getWorkspaceProxies
+          : API.getWorkspaceProxyRegions;
+
+        const resp = await apiCall();
         return resp.regions;
       },
     }),

site/src/contexts/auth/RequireAuth.tsx

@@ -1,6 +1,6 @@
 import { type FC, useEffect } from "react";
 import { Outlet, Navigate, useLocation } from "react-router-dom";
-import { axiosInstance } from "api/api";
+import { API } from "api/api";
 import { isApiError } from "api/errors";
 import { Loader } from "components/Loader/Loader";
 import { ProxyProvider } from "contexts/ProxyContext";
@@ -18,6 +18,7 @@ export const RequireAuth: FC = () => {
       return;
     }
 
+    const axiosInstance = API.getAxiosInstance();
     const interceptorHandle = axiosInstance.interceptors.response.use(
       (okResponse) => okResponse,
       (error: unknown) => {

site/src/contexts/useProxyLatency.ts

@@ -1,6 +1,6 @@
 import PerformanceObserver from "@fastly/performance-observer-polyfill";
 import { useEffect, useReducer, useState } from "react";
-import { axiosInstance } from "api/api";
+import { API } from "api/api";
 import type { Region } from "api/typesGenerated";
 import { generateRandomString } from "utils/random";
 
@@ -197,6 +197,7 @@ export const useProxyLatency = (
     // The resource requests include xmlhttp requests.
     observer.observe({ entryTypes: ["resource"] });
 
+    const axiosInstance = API.getAxiosInstance();
     const proxyRequests = Object.keys(proxyChecks).map((latencyURL) => {
       return axiosInstance.get(latencyURL, {
         withCredentials: false,