Remove IContainerRuntimeOptions.flushMode

[markfields]

We are removing IContainerRuntimeOptions.flushMode. This option had let an application specify whether to flush ops "immediately" (literally 1-by-1) or "turn-based" (batched by JS turn). But Immediate is deprecated and not to be used.

Since Immediate is deprecated, there is only one choice, which is the default TurnBased. So we can simply remove this option.

Approach

No one should be using Immediate anymore, it's been deprecated since Feb 2024 (see #19753 and #19963)

Dependencies

Merge #23272

Compatibility Concerns

We still need to support Immediate mode, for interop with 1.x clients, but that is configured from within FF code so we are exposing Immediate mode only internally, not in legacy-alpha APIs anymore.

Phases

Note: Once 1.x compat mode is no longer supported, we'll remove this feature altogether.

Expected Timeline

To be removed post 1/6/25, to land in 2.20.0

Links

• Deprecation PR announcing the removal: Deprecate IContainerRuntimeOptions.flushMode #23288
• Task tracking the removal: AB#26496