`ProfileFileCredentialsProvider` ignores profile `use_fips_endpoint` for STS

[hligit]

When using ProfileFileCredentialsProvider::builder() with profile files and profile name supplied programmatically, a profile-level use_fips_endpoint = true setting is not propagated to the internal STS client used for AssumeRole during credential role chaining.

As a result, STS requests go to a non-FIPS endpoint even though the selected profile enables FIPS.

Expected behavior

If the selected profile contains:

[profile fips-test]
use_fips_endpoint = true
region = us-east-1

then the internal STS client used by ProfileFileCredentialsProvider for AssumeRole should use a FIPS endpoint, e.g.:

https://sts-fips.us-east-1.amazonaws.com/

or equivalent FIPS endpoint resolution.

Actual behavior

The internal STS client uses the non-FIPS endpoint:

https://sts.us-east-1.amazonaws.com/

Example code demonstrating the issue

Cargo.toml.txt
main.rs.txt