Add client for the latency1 protocol

[robertodauria]

Adds a self-contained client for the latency1 protocol.

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This change is 

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Totals
Change from base Build 7476920368:	0.2%
Covered Lines:	877
Relevant Lines:	1253

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[stephen-soltesz]

-- thanks!

Reviewed 2 of 2 files at r1.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @robertodauria)

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cmd/msak-latency/main.go line 130 at r1 (raw file):

		// If a server was provided, use it.
		var err error
		authorizeURL = &url.URL{

I've become a big fan of using flagx.URL for user-specified scheme, servers (maybe path) -- as in minimal-download. What do you think of that approach?

In this case, I might probably add one flag to replace the current server/scheme flags and generate these two urls with specific paths at run time.

[stephen-soltesz]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @robertodauria)