feat(auth): add support for IAM profile management and flare endpoints (#7659)

## Problem
The webview does not support IAM credentials input and endpoint to LSP
does not support IAM credentials and IAM profiles.

## Solution
This is part of #7507.

- Add IAM credentials option and form to webview
- Modify AuthUtils to switch between SsoLogin and IamLogin strategies
- Add startIamCredentialSetup in backend_amazonq

Meanwhile, we are making changes to language-servers and
language-server-runtimes such that authentication for IAM credentials
can happen on Flare side.

working branches:

https://github.com/liramon1/language-server-runtimes/tree/feature/flare-iam
https://github.com/liramon1/language-servers/tree/liramon/flare-iam

Current PR built upon flare-mega branch and is working to merge with
flare-mega branch. This PR fails a web test that flare-mega branch is
also failing, at the same place.

---

- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: yuxianrz

package-lock.json

@@ -22,5 +22,5 @@ export async function loginToIdC() {
         )
     }
 
-    await AuthUtil.instance.login(startUrl, region)
+    await AuthUtil.instance.loginSso(startUrl, region)
 }

packages/amazonq/test/e2e/amazonq/utils/setup.ts

@@ -26,11 +26,11 @@ describe('RegionProfileManager', async function () {
 
     async function setupConnection(type: 'builderId' | 'idc') {
         if (type === 'builderId') {
-            await AuthUtil.instance.login(constants.builderIdStartUrl, region)
+            await AuthUtil.instance.loginSso(constants.builderIdStartUrl, region)
             assert.ok(AuthUtil.instance.isSsoSession())
             assert.ok(AuthUtil.instance.isBuilderIdConnection())
         } else if (type === 'idc') {
-            await AuthUtil.instance.login(enterpriseSsoStartUrl, region)
+            await AuthUtil.instance.loginSso(enterpriseSsoStartUrl, region)
             assert.ok(AuthUtil.instance.isSsoSession())
             assert.ok(AuthUtil.instance.isIdcConnection())
         }