channelz: use atomic instead of mutex

[lyuxuan]

No description provided.

[menghanl]

Reviewed 4 of 4 files at r1.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @lyuxuan)

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clientconn.go, line 726 at r1 (raw file):

}

type channelzData struct {

Comment why this struct is necessary.

And move to another file since it's used by both client and server.

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clientconn.go, line 730 at r1 (raw file):

	callsFailed         int64
	callsSucceeded      int64
	lastCallStartedTime int64

Comment what the format is and why.

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clientconn.go, line 761 at r1 (raw file):

	channelzID int64 // channelz unique identification number
	czmu       sync.RWMutex

Remove this mutex

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internal/transport/http2_client.go, line 117 at r1 (raw file):

}

type channelzData struct {

Move to another file

[menghanl]

Reviewable status: 2 of 6 files reviewed, 3 unresolved discussions (waiting on @menghanl and @lyuxuan)

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rpc_util.go, line 761 at r2 (raw file):

	callsFailed         int64
	callsSucceeded      int64
	lastCallStartedTime int64

Comment the format and reason for this.

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internal/transport/transport.go, line 752 at r2 (raw file):

	msgSent           int64
	msgRecv           int64
	lastMsgSent       int64

Comment the format and reason for this.
And add "Time" to the variable name so it's clear?

[menghanl]

Reviewed 1 of 4 files at r2, 4 of 4 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved