[docs] Verify gflags that are runtime-settable and add to configuration pages.

[stevebang]

The yb-ts-cli utility is useful for setting gflags/options during runtime. And, the utility has a --force option to change flags even if they are not runtime-settable.

In the code (according to @bmatican), TAG_FLAG is how we add special metadata to each flag, and runtime is one of them. By default, if not specified, it is NOT runtime. But we also likely don’t do a stellar job at marking them as such.

Someone needs to review the TAG_FLAG settings for the gflags/options so that we can document which options can safely be changed during runtime.

[stevebang]

@ameyb In the context of Yugabyte Platform, this would be valuable so that users know what they can configure during runtime versus requiring a restart.

[hari90]

The information is available in each build. Files master_flags.xml and tserver_flags.xml have the runtime tag info for each flag in their corresponding process.