Add user-agent to all http clients using RawClientHttpRequestSettings.

[TingluoHuang]

Before:

User-Agent: VSServices/2.312.0.0
(NetStandard; Darwin 23.3.0 Darwin Kernel Version 23.3.0: Wed Dec 20 21:30:44 PST 2023; root:xnu-10002.81.5~7/RELEASE_ARM64_T6000)

After:

User-Agent: VSServices/2.312.0.0 (NetStandard; Darwin 23.3.0 Darwin Kernel Version 23.3.0: Wed Dec 20 21:30:44 PST 2023; root:xnu-10002.81.5~7/RELEASE_ARM64_T6000) 
GitHubActionsRunner-osx-arm64/2.312.0
HttpProxyConfigured/True
ClientId/1ef6c146-8b46-40ab-b57f-0871bfc614b5 
RunnerId/2 
GroupId/1 
CommitSHA/2e8e48f2a53cf8077b7d27d7064943622ad42786 
OrchestrationId/aee4139d-34c5-429f-8ab3-07c2b6058396.build_and_test.relwithdebinfo.main.main.__default
(Darwin 23.3.0 Darwin Kernel Version 23.3.0: Wed Dec 20 21:30:44 PST 2023; root:xnu-10002.81.5~7/RELEASE_ARM64_T6000)

So we can have better correlation better telemetry and the runner.

Fixing: https://github.com/github/actions-results-team/issues/2204