project: Rename build options

Following the new meson porting guidelines, this patch renames the
build options. The list of changes is as follows:

- Remove the enable prefix from boolean options.
- The character separator from multi-word options has been changed
  to underscore.
1 job for new_guidelines in 6 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
passed #1535