Replacing Len function with DATALENGTH function

[rajithaalurims]

Description

"CONSTRAINT CHK_TokenSearchParam_CodeOverflow CHECK (LEN(Code) = 256 OR CodeOverflow IS NULL)" is failing while inserting data.
Code value that is greater than 256 characters and has empty spaces at the end when we split it into Code and CodeOverFlow causes the issue.
CHECK (LEN(Code) = 256 - SQL LEN function returns length of the value removing trailing blanks.

This PR has changes to replace LEN function with DATALENGH to get correct bytes stored.

Related issues

Addresses [issue #158203].

Testing

Manually verified the scenario by testing with same data that is breaking before the change
Existing unit and E2E tests

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 65 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, Build, Dependencies, Enhancement, New-Feature or Documentation
• Tag the PR with Open source, Azure API for FHIR (CosmosDB or common code) or Azure Healthcare APIs (SQL or common code) to specify where this change is intended to be released.
• Tag the PR with Schema Version backward compatible or Schema Version backward incompatible or Schema Version unchanged if this adds or updates Sql script which is/is not backward compatible with the code.
• When changing or adding behavior, if your code modifies the system design or changes design assumptions, please create and include an ADR.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Patch|Skip|Feature|Breaking (reason)