Addition of waitSig pprof argument to start recording on USR1

[frouioui]

Description

After running long benchmarks while profiling Vitess, the profiles start to get too big for go tool pprof and return an EOF error. To counterattack this issue, we decided to stop recording at any given time by using #7594, and without affecting the benchmarks.

However, we also want to control when to start recording. In the case of the benchmarks, we often have long preparation times where we insert and "warm-up" the system before practicing the actual benchmark. This is what this pull request brings: start recording at any given moment based on a received signal (USR1).

cc @vmg

Related Issue(s)

• Large profiles are not recorded properly arewefastyet#53
• pprof: allow stopping profiling early with a signal #7594

Checklist

• Should this PR be backported?
• Tests were added or are not required
• Documentation was added or is not required

Impacted Areas in Vitess

Components that this PR will affect:

• Query Serving
• VReplication
• Cluster Management
• Build/CI
• VTAdmin

[vmg]

Very nice refactoring.