Add RCUTILS_NO_PROCESS_SUPPORT option to build without fork/exec/wait

[jimmy-mcelwain]

Addresses micro-ROS/micro_ros_setup#813

This is my first PR to rcutils, I am not particularly familiar with the repo and I did use AI to generate some of the code. But I tried to make sure that the new option is like the other options, and I have built and made sure that with the flag set that it runs on my machine (YRC1000 with a custom micro-ros build).

With RCUTILS_NO_PROCESS_SUPPORT not set, it does not compile for my target machine, as expected. Though it works on my dev PC either way. I am of course not using rcutils_start_process or rcutils_process_wait in any MotoROS2 code, I just did this so I could get rid of the symbols and compile.

I know that the colcon metas will need to be updated with this new option, but I am not familiar enough with the different micro-ros platforms to know which ones do and which ones should be set to ON and which ones should be set to OFF.

I had to move a header. Originally I just included configuration_flags.h directly but the linter didn't like that.

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