MSAL can consider using lazy import for `request`, `jwt`

[jiasli]

Describe the bug

Importing MSAL is can cost ~300ms on Windows due to some heavy libraries like request and jwt:

python -X importtime -c "import msal"  2>perf.log; tuna .\perf.log

MSAL can consider using lazy import for these libraries so that importing MSAL can be lightweight. (Azure CLI lazily imports MSAL: Azure/azure-cli#19898)

[rayluo]

Jiashuo Li (@jiasli) , your screenshot indicated that the requests and jwt combined for 2/3 of the msal import time. The PR above is able to remove those 2 parts from the tuna chart, however the overall import time was only cut short by 1/3, rather than 2/3. Still better than the current situation. :-/