Implement propagation of x-goog-spanner-request-id gRPC header on every call

[odeke-em]

This is a feature request to implement propagation of x-goog-spanner-request-id gRPC header on every call.

Reasoning

x-goog-spanner-request-id allows propagation of an ID that'll be correlated between client and server calls. We can't rely on trace headers because they are sampled, convoluted through a bunch of infrastructure so Google Engineering asked that we craft up a better mechanism. The value will allow tracking the operations of an RPC even through retries

Requirements

Each x-goog-spanner-request-id requires the following fields

• Version of the specification being implemented: ordinal number: 1 for version 1
• random Uint64 for the process' lifetime
• ID of the SpannerClient being used
• channelID for the gRPC channel being used
• Nth Request Count: nthReq
• RPC attempt number for nthReq

Specification

Please reference https://orijtech.notion.site/x-goog-spanner-request-id-always-on-gRPC-header-to-aid-in-quick-debugging-of-errors-14aba6bc91348091a58fca7a505c9827?pvs=4

Reference implementation

I built a Go reference implementation at googleapis/google-cloud-go#11048

/cc @tharoldD