Rename fluoride_common_options into bluetooth_cflags

fluoride_common_options are not only used inside fluoride but all
bluetooth cc targets so use the prefix `bluetooth` instead of
`fluoride`.

Also use a less generic name `common_options` -> `cflags` to
document what contains this default for the rules using this default

Test: mma packages/modules/Bluetooth
Bug: 279502784
Change-Id: Ic3b7a62bc97f8eab24d9130fbe2e2367596bdc9b