[extension/cgroupruntime]: Initial implementation (open-telemetry#35472)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

This PR adds the initial implementation of a new component to
dynamically set the values of `GOMEMLIMIT` and `GOMAXPROCS` used by the
Go runtime. Those values are normally manually aligned with the cgroup
resource limit to prevent cpu throttling or out of memory scenarios.

The component would ease the manual steps of configuring these
environment variables in K8s deployments (e.g Helm
[templates](https://github.com/open-telemetry/opentelemetry-helm-charts/blob/main/charts/opentelemetry-collector/templates/_helpers.tpl#L169))
in addition to have fine-grained values (e.g. 90% of the resource memory
limits).

**Link to tracking Issue:** <Issue number if applicable>
open-telemetry#30289

**Testing:** <Describe what testing was performed and which tests were
added.> Unit testing for the component has been added (config and
extension start/stop). But ideally, an integration test that actually
asserts the runtime modifications should be added as well. The extension
relies on "github.com/KimMachineGun/automemlimit/memlimit" and
"go.uber.org/automaxprocs/maxprocs" packages for the runtime
modifications, but they don't provide a way to mock the "cgroups" file
system which is the one they read to get the resource quota limits.

- Automemlimit package tests expect to run in a cgroup environment:
https://github.com/KimMachineGun/automemlimit/blob/main/memlimit/cgroups_test.go#L18
- Automaxprocs does not expose the cpu quota retrieval
https://github.com/uber-go/automaxprocs/blob/master/maxprocs/maxprocs.go#L41

Any suggestion on how to perform this integration tests in the contrib
repository? One possibility is to use the
https://github.com/containerd/cgroups package to set the quota, but this
requires privileged permissions (also in the GHA)

**Documentation:** <Describe the documentation added.>

---------

Co-authored-by: Pablo Baeyens <[email protected]>

Author: 2 people

.chloggen/add_cgroupruntime_extension.yaml

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+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: extension/cgroupruntime
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Initial implementation for cgroupruntime extension.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [30289]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []