Several behaviors in common LiveLink code that were intended to be specific to LiveLink Hub were previously controlled by the WITH_LIVELINK_HUB preprocessor definition, which precluded sharing a build environment with the rest of the editor.
This CL replaces those preprocessor conditionals with appropriate config directives that are overridden in `Programs/LiveLinkHub/Config/DefaultEngine.ini`.
#jira UE-214787
#rb jason.walter, jeremie.roy
[CL 34681560 by zach brockway in ue5-main branch]
Adds support for building a version of LiveLink Hub configured as TargetType.Editor, and support for staging it with a custom subclass of MakeCookedEditor.
By sharing a build environment with the UnrealEditor target, we will be able to create a standalone distribution of LiveLink Hub that is ABI-compatible with plugins built and packaged from the standard UE distribution. This achieves our goal of supporting dynamically loaded third-party vendor plugins.
This also reduces build and iteration times by sharing modules with UE, and once it replaces the monolithic program target, will reduce the size of the LiveLinkHub executable in the UE distribution from ~237 MB to ~1 MB.
Example staging invocation: `RunUAT MakeLiveLinkHubEditor -project=Engine\Source\Programs\LiveLinkHubEditor\LiveLinkHubEditor.uproject -build -skipcook -stage [-nodebuginfo]`.
(This CL additionally introduces support for staging the existing program target with `RunUAT BuildCookRun -project=Engine\Programs\LiveLinkHub\LiveLinkHub.uproject -build -skipcook -stage [-nodebuginfo]`; however, it requires one additional change to further restrict `OptedInModulePlatforms` in LiveLinkHub.Target.cs, currently commented out due to uncertain impact to existing build automation.)
#jira UE-214748
#rb jason.walter, jeremie.roy
[CL 34680043 by zach brockway in ue5-main branch]
