Allow pipeline creation rate limit to be disabled for some projects

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/352232#note_972620369

We want to enable ci_enforce_throttle_pipelines_creation for almost all the projects on .com and using the standard rollout process with a single feature flag doesn't work as expected:

By default you cannot selectively disable a feature flag by actor.

# This will not work how you would expect.
/chatops run feature set some_feature true
/chatops run feature set --project=gitlab-org/gitlab some_feature false

However, if you add two feature flags, you can write your conditional statement in such a way that the equivalent selective disable is possible.

Feature.enabled?(:a_feature, project) && Feature.disabled?(:a_feature_override, project)

# This will enable a feature flag globally, except for gitlab-org/gitlab
/chatops run feature set a_feature true
/chatops run feature set --project=gitlab-org/gitlab a_feature_override true

In this MR I'm adding the override feature flag and updating the logged message to indicate if the log entry was part of a throttle pipeline request or not.

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