feat: remove config object cloning to fix TokenCredential issues

[BrandonNoad]

What this does:

Config objects are no longer cloned. If a TokenCredential was being passed as config.authentication.options.credential, it wasn't being handled correctly (see #1745 (comment) for more details)

Related issues:

Fixes #1745

Pre/Post merge checklist:

• Update change log

[BrandonNoad]

The README mentions that the config is cloned a few different times e.g., "It is safe to pass read-only config objects to the library; config objects are now cloned". Not sure how you want to handle this re: breaking changes

[dhensby]

Thanks for taking the time to do this, please can you reword the commit to meet the commit conventions (https://www.conventionalcommits.org/en/v1.0.0/); I'd suggest this is feat:.

RE docs, yeah - we should change that to remove the mention that we clone the config object and that any subsequent modifications by reference will lead to undefined behaviour.