Migrate sts code to AWS SDK v2

[nrb]

Update calls in the following packages and files. Note that this is not necessarily an exhaustive list.

./pkg/cloud/services/sts/mock_stsiface
./pkg/cloud/services/sts/mock_stsiface/stsiface_mock.go

[damdo]

See examples on how to migrate here: #5389

[serngawy]

/assign @serngawy

[serngawy]

/unassign @serngawy

[alexander-demicev]

/assign