Sort is crashing when Organization (any resource) is searched using chained search param and sort

[rajithaalurims]

Description

Ex: https://ihealth-pie.fhir.azurehealthcareapis.com/Organization?partof.name=ABC&_sort=name throws Unknown error instead of returning results back.
As part of this work item, code was added in SortRewriter class to return null expression when sort field is already part of search filter name, which is causing failure in case of chained expression.
I modified code to use the expression as it is in chained expression part.

Related issues

AB#94770

Testing

Created test data and tested below URLs.
https://localhost:44348/Organization?partof.name=Test&_sort=name - should return results without failing
https://localhost:44348/Organization?name=Test&_sort=name - should return results as before
https://localhost:44348/Patient?organization.name=Mi&_sort=name - should return results without failing
https://localhost:44348/Patient?name=Mi&_sort=name - should return results as before

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 50 characters
• Add a milestone to the PR for the sprint that it is merged (i.e. add S47)
• Tag the PR with the type of update: Bug, Dependencies, Enhancement, or New-Feature
• Tag the PR with Azure API for FHIR if this will release to the Azure API for FHIR managed service (CosmosDB or common code related to service)
• Tag the PR with Azure Healthcare APIs if this will release to the Azure Healthcare APIs managed service (Sql server or common code related to service)
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Patch|Skip|Feature|Breaking (reason)