Support setting ballast size in percentage of total Mem in ballast extension

[mxiamxia]

Descritpion:
Enhance the current ballast extension which is to set memory ballast for the collector process. And we'll remove --mem-ballast-size-mib support from command line later.

The changes,
Added new configuration size_in_percentage which can dynamically set ballast size based on the total memory of the running environments. (hosts, Docker, K8s, etc)

Sample Config,

extensions:
  memory_ballast:
    size_in_percentage: 20

How ballast size is calculated by percentage setup
When size_in_percentage is enabled with the value(1-100), the ballast_size will be calculated by
size_in_percentage * totalMemory. The totalMemory will be calculated for hosts and containers(in docker, k8s, etc) by the following steps,

1. Look up Memory Cgroup subsystem where the collector is running on(it could be container, VM or bare metal host), check if there is total memory limitation has been set for the collector process.
   The total assigned memory for the process is in memory.limit_in_bytes file under cgroup (eg, /sys/fs/cgroup/memory/memory.limit_in_bytes).

2. If memory.limit_in_bytes has a positive value other than 9223372036854771712. The ballest_size
   will be calculated by memory.limit_in_bytes * size_in_percentage. Else If memory.limit_in_bytes value is 9223372036854771712(0x7FFFFFFFFFFFF000), it indicates there is no memory limit has been set for the collector process in cgroup. Then the totalMemoery will be determined in the next step

3. if there is no memory limit set in cgroup for the collector process or container where the collector is running. The total memory will be calculated by github.com/shirou/gopsutil/mem which is supported in multiple OS systems.

Link to tracking Issue:
#2516

Test:
Tested locally on EC2, Docker and K8S for ballast_size_in_percentage configuration

[alolita]

@mxiamxia can you fix these failing tests. Thx.

[punya]

@Aneurysm9 @anuraaga could you please take a look?

[anuraaga]

Cool feature

[alolita]

@anuraaga @Aneurysm9 can you please re-review? The tests are now passing.

[mxiamxia]

Hi @anuraaga @bogdandrutu @tigrannajaryan @rakyll , PTAL! Thanks.

[bogdandrutu]

@tigrannajaryan @rakyll PTAL, will merge tomorrow otherwise

[tigrannajaryan]

LGTM, except I have just found we also have a built-in ballast implementation in

opentelemetry-collector/service/collector.go

Line 317 in 6cafee9

func (col *Collector) createMemoryBallast() ([]byte, uint64) {

I am confused. Why do we have 2 implementations? Are they related or competing?

[mxiamxia]

opentelemetry-collector/service/collector.go

This old one is taking the ballast size input from the command line. I will send another PR to deprecate the old ballast memory creation implementation.

[alolita]

@bogdandrutu this PR is ready to be merged. :-)