AXL release for SCR v3.1

[CamStan]

See SCR v4.0 project: https://github.com/orgs/LLNL/projects/26

Process

• Merge any outstanding PRs, close any outstanding issues
• Pass GitLab CI tests*
• Update the version number in the code, CMakeLists.txt, and any references to dependency versions
• Create a PR with these changes
• Merge the PR
• Tag a release on GitHub
• write some release notes
• Update the spack package: Update hash for download; Update dependency versions

[gonsie]

@CamStan Axl is ready for these steps, both #131 and #145 and WIPs.

[CamStan]

*All CI tests passed on x86_64 system, 1 failed on power9.

The test waits 3 seconds before initiating a bbapi transfer cancel, but all the files had already copied by then. So the issue here was with the test itself.
In the future, adjusting the test or scaling up might resolve this.

test 5
    Start 5: bbapi_cancel_test
5: Test command: /g/g0/stanavig/.jacamar-ci/builds/xYGwyxK_/002/gitlab/ecp-veloc/AXL/build/test/test_axl.sh "-n" "300" "-c" "3" "bbapi"
5: Test timeout computed to be: 10000000
5: Testing bbapi transfer cancel after 3 seconds...	failure.  Files were all copied before the cancel
5/9 Test #5: bbapi_cancel_test ................***Failed    6.15 sec