[WIP] Add "thrift_requester_service_name" metric to thrift context handler

[wlwanpan]

Closes #

💸 TL;DR

Proposing "thrift_requester_service_name" metric to be added to the thrift context handler.

Note: this is a draft PR and if accepted, I'll be sending a format spec change request.

📜 Details

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🧪 Testing Steps / Validation

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