Move feature-flags from CI to nightly

[hjdivad]

We depend on the Ember Data CUSTOM_MODEL_CLASS feature flag, which is
off by default in 3.24.0, and on by default in 3.28.0. We used to have
to test this feature flag against canaries prior to 3.28.0's release,
but no longer.

We no longer depend on any optional feature flags, but still run the job
to ensure that enabling optional features in Ember Data does not
otherwise break ember-m3.

The job will be red right now because we currently are not compatible
with 4.0.0 and also not with canary releases of ember and ember-data.

Co-Authored-By: Larry Yu laryu@linkedin.com

[github-actions]

Performance Report for a0fee8d

Scenario - materializing-lots: ☑️ Performance is stable

☑️ duration
phase no difference [-51ms to 46ms]
☑️ Phase [navigationStart] => [start-loading]
phase no difference [-7ms to 5ms]
☑️ Phase [start-loading] => [pushed-payload]
phase no difference [-51ms to 17ms]
☑️ Phase [pushed-payload] => [end-loading]
phase no difference [-13ms to 49ms]
☑️ Phase [end-loading] => [Test End]
phase no difference [0ms to 2ms]

Scenario - materializing-small: ☑️ Performance is stable

☑️ duration
phase no difference [-4ms to 10ms]
☑️ Phase [navigationStart] => [start-loading]
phase no difference [-4ms to 6ms]
☑️ Phase [start-loading] => [pushed-payload]
phase no difference [-2ms to 2ms]
☑️ Phase [pushed-payload] => [end-loading]
phase no difference [-1ms to 3ms]
⚠️ Phase [end-loading] => [Test End]
phase estimated regression +1ms [0ms to 2ms] OR +2.42% [0.22% to 4.54%]

Scenario - rendering: ☑️ Performance is stable

☑️ duration
phase no difference [-24ms to 7ms]
☑️ Phase [navigationStart] => [start-loading]
phase no difference [-8ms to 2ms]
☑️ Phase [start-loading] => [pushed-payload]
phase no difference [-3ms to 1ms]
☑️ Phase [pushed-payload] => [end-loading]
phase no difference [-1ms to 0ms]
☑️ Phase [end-loading] => [Test End]
phase no difference [-15ms to 9ms]

[larry-x-yu]

LGTM