SSO: does not cancel timeout if "AWS: Choose AWS Profile" switches to different profile

steps to reproduce:

1. run `AWS: Choose AWS Profile`
2. select a SSO profile
3. do _not_ complete the SSO flow
4. run `AWS: Choose AWS Profile` and choose a different profile
5. wait a long time
5. the SSO timeout from the first attempt eventually times out, and an error is shown

Start by tracing the `AWS: Choose AWS Profile` command through the SSO flow and its timeout handling. Reproduce the two-profile sequence, then verify that switching profiles prevents the abandoned first SSO attempt from later displaying its timeout error.

Written by the indexing model from the issue text.