[Fargate] [Kernel.pid_max]: To be able to set kernel.pid_max in systemControls

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**Tell us about your request**
I want to be able to control and make the kernel.pid_max higher in a Fargate instance, because the current pid_max value is what controls the number of LDW, lightweight threads a program can create.
I'm running load test in Fargate and I want to be able to start a lot of threads.

**Which service(s) is this request for?**
Fargate

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
It's impossible to start a serious load test in Fargate because at certain high Request Per Second, e.g. 10k RPS, my java program hits the current Kernel PID Max of around 30k threads. There's no way I can increase this value and my program shuts down.

**Are you currently working around this issue?**
I cannot work around it, I tried multiple things such as increasing memory etc, but all that does is increase other system limit but not PID Max

Start with the request to control kernel.pid_max in Fargate systemControls and the described Java load-test failure at around 30k threads. No repository files, tests, or entry points are named; done would require Fargate to support raising this limit or documenting the supported behavior.

Written by the indexing model from the issue text.