Doc consistenty review updates (#31332)

* readme updates

* docs.microsoft.com -> learn.microsoft.com

* sentence case

* ChainedTokenCredential example

* sentence case

* cleanup links

* Add AzurePowerShellCredential

* replace AAD with Azure AD

* remove please

* the Azure Cloud -> Azure

* remove extra word

* fix logging links, remove VisualStudioCredential from the list

* fix list tag

* Add ClientAssertionCredential troubleshooting

* minor formatting fixes

* sentence case headings

* alphabetize

* replace quotation marks

* docs.microsoft -> learn.microsoft

* fix anchors

* sentence case TOC

* Remove locale from url

* Update sdk/identity/azure-identity/README.md

Co-authored-by: Scott Addie <[email protected]>

* Update sdk/identity/azure-identity/README.md

Co-authored-by: Scott Addie <[email protected]>

* Update sdk/identity/azure-identity/README.md

Co-authored-by: Scott Addie <[email protected]>

* Update sdk/identity/azure-identity/README.md

Co-authored-by: Scott Addie <[email protected]>

* Update sdk/identity/azure-identity/TROUBLESHOOTING.md

Co-authored-by: Scott Addie <[email protected]>

* Update sdk/identity/azure-identity/README.md

Co-authored-by: Scott Addie <[email protected]>

* remove extraneous package mention

* Apply suggestions from code review

Co-authored-by: Scott Addie <[email protected]>

Co-authored-by: Scott Addie <[email protected]>