chore(profiling): pin version of echion dependency [backport 2.7] (#9177

)

Backport b860ab0 from #9142 to 2.7.

Profiling introduced a "stack v2" feature recently in order to address
reports of segmentation faults.

As part of this, we rely on the
[echion](https://github.com/P403n1x87/echion) codebase. We'll be making
changes to echion in response to certain customer issues, with the
corresponding fixes needing to be backported.

This PR simply tightens up the build process for stack v2 in order to
pin the dependency version more precisely. It's a developmental PR for
future fixups.

## Checklist

- [X] Change(s) are motivated and described in the PR description
- [X] Testing strategy is described if automated tests are not included
in the PR
- [X] Risks are described (performance impact, potential for breakage,
maintainability)
- [X] Change is maintainable (easy to change, telemetry, documentation)
- [X] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed or label `changelog/no-changelog` is set
- [X] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/))
- [X] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
- [X] If this PR changes the public interface, I've notified
`@DataDog/apm-tees`.

## Reviewer Checklist

- [x] Title is accurate
- [x] All changes are related to the pull request's stated goal
- [x] Description motivates each change
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- [x] Testing strategy adequately addresses listed risks
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] Release note makes sense to a user of the library
- [x] Author has acknowledged and discussed the performance implications
of this PR as reported in the benchmarks PR comment
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: David Sanchez <[email protected]>

ddtrace/internal/datadog/profiling/stack_v2/CMakeLists.txt

@@ -26,10 +26,11 @@ if (NOT Python3_INCLUDE_DIRS)
 endif()
 
 # Add echion
+set(ECHION_COMMIT "d69048b63e7d49091659964915eb52ff0ced9fc8" CACHE STRING "Commit hash of echion to use")
 FetchContent_Declare(
     echion
     GIT_REPOSITORY "https://github.com/sanchda/echion.git"
-    GIT_TAG "sanchda/more_rendering"
+    GIT_TAG ${ECHION_COMMIT}
 )
 FetchContent_GetProperties(echion)
 if(NOT echion_POPULATED)