Fix Remote Access settings in secure mode (#18127)
Closes #18107
Summary of the issue:
Remote Access's settings were improperly disabled in secure mode, including disabling options that could be useful in secure mode.
Description of user facing changes
Most of Remote Access's settings are visibly disabled in secure mode, and cannot be activated with object navigation.
The "Confirm before disconnecting when controlled" option is still enabled in secure mode.
There is no banner notice on Remote Access's settings page when in secure mode.
Description of development approach
Change the approach for disabling the config items. Rather then them all being in a parent grouping, recursively disable the children of the containing sizer.
To keep some options enabled, maintain a set of options that make sense in secure mode, and exclude those options when disabling everything.
Remove the method to create the read only banner.
Refactor things to remove the no-longer needed containing static box sizer helper.
