refactor(amazonq): change IAM and SSO service references

[liramon1]

Problem

The agentic bundle for the CodeWhisperer LSP only supports SSO. If language clients want it to consume IAM credentials, they must start a completely separate bundle which includes the IAM implementation of the CodeWhisperer LSP. This prevents clients from seamlessly switching authentication methods at runtime.

Solution

This is part of #1936.

This PR changes references from the IAM/SSO implementations of CodeWhispererService, StreamingClientService, and AmazonQServiceManager to the unified implementations from the prior PRs.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 61.00746% with 209 lines in your changes missing coverage. Please review.

Please upload report for BASE (feature/flare-iam-base@1491f4f). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...p-codewhisperer/src/shared/codeWhispererService.ts	36.12%	168 Missing ⚠️
...codewhisperer/src/shared/streamingClientService.ts	84.90%	16 Missing ⚠️
...rer/src/language-server/chat/chatSessionService.ts	50.00%	4 Missing ⚠️
...er/securityScan/codeWhispererSecurityScanServer.ts	0.00%	4 Missing ⚠️
...r/aws-lsp-codewhisperer/src/shared/proxy-server.ts	0.00%	4 Missing ⚠️
...nguage-server/agenticChat/agenticChatController.ts	72.72%	3 Missing ⚠️
...r/localProjectContext/localProjectContextServer.ts	0.00%	3 Missing ⚠️
...language-server/netTransform/netTransformServer.ts	0.00%	3 Missing ⚠️
...rc/language-server/agenticChat/tools/toolServer.ts	0.00%	2 Missing ⚠️
...ge-server/inline-completion/codeWhispererServer.ts	90.90%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@                    Coverage Diff                    @@
##             feature/flare-iam-base    #1961   +/-   ##
=========================================================
  Coverage                          ?   65.82%           
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  Files                             ?      237           
  Lines                             ?    50675           
  Branches                          ?     3400           
=========================================================
  Hits                              ?    33357           
  Misses                            ?    17258           
  Partials                          ?       60           

Flag	Coverage Δ
unittests	65.82% <61.00%> (?)

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