New VReplication lag metric

[rohit-nayak-ps]

Description

Adds a new metric to display vreplication lags in the form of a gauge for easier display in VTAdmin.

Example:

"VReplicationLag": {"1":[1.6,4.8,4.8,4.8,4.8,10.8,13.8,9,4.8,4.8,4.6,4.8,9.6,5.2,10.2,6.4,5.8,6.4,6.4,6.4,6.4,6.4,6.4,6.4,6.4,6.4,7.2,6.4,6.4,6.4,6.4,6.4,6.4,6.4,6.4,9.8,8,8,8.2,7.6,8.4,7.2,8,6.8,6.4],
"10":[4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.6,4.8,4.8,5.2,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,0,0,0,0,0,0,0,0,0],
"11":[4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.4,4.8,4.8,5.2,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,5,0,0,0,0,0,0,0,0,0],
"All":[4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.8,4.6,4.8,4.8,5.2,4.8,4.8,4.8,4.8,4.8,4.

Signed-off-by: Rohit Nayak rohit@planetscale.com

[doeg]

I tried this out locally + it worked as promised! 🎉 Thanks, this will be great to have.