Promote execution_graph_log to stable

### Description of the bug:

`--experimental_execution_graph_log` and `--experimental_execution_graph_log_dep_type` were introduced in Bazel 6.

Based on the history of https://github.com/bazelbuild/bazel/commits/master/src/main/java/com/google/devtools/build/lib/runtime/ExecutionGraphModule.java I believe this feature is now stable enough to permit production usage (for example, instrumenting a CI system to ["understand the drag that is added by a node on the critical path"](https://bazel.build/advanced/performance/build-performance-metrics#execution-graph-log) )

@justinhorvitz you have been the author of recent changes, can you confirm/deny if these experimental flags could be stable?

### Which category does this issue belong to?

Core

Start by reviewing src/main/java/com/google/devtools/build/lib/runtime/ExecutionGraphModule.java and its recent history, focusing on --experimental_execution_graph_log and --experimental_execution_graph_log_dep_type. Confirm whether the execution graph logging feature is ready for production use and identify the project changes needed to make the flags stable.

Written by the indexing model from the issue text.