[cmake] add interface libraries ot-config-(ftd|mtd|radio) (#8190)

This allows for more granular control of any configuration which
might need to be incorporated in the core library build.

examples/apps/cli/ftd.cmake

@@ -44,6 +44,7 @@ target_link_libraries(ot-cli-ftd PRIVATE
     ${OT_PLATFORM_LIB_FTD}
     openthread-cli-ftd
     ${OT_MBEDTLS}
+    ot-config-ftd
     ot-config
 )
 

examples/apps/cli/mtd.cmake

@@ -44,6 +44,7 @@ target_link_libraries(ot-cli-mtd PRIVATE
     ${OT_PLATFORM_LIB_MTD}
     openthread-cli-mtd
     ${OT_MBEDTLS}
+    ot-config-mtd
     ot-config
 )
 

examples/apps/cli/radio.cmake

@@ -48,6 +48,7 @@ target_link_libraries(ot-cli-radio PRIVATE
     ${OT_PLATFORM_LIB_RCP}
     openthread-cli-radio
     ${OT_MBEDTLS_RCP}
+    ot-config-radio
     ot-config
 )