Add a fuzzer in bluetooth gd for l2cap dynamic channel allocator

Initialized fuzz test for Bluetooth GD library. There is one fuzz target
gd/fuzz_test.cc and it will call all fuzz tests in gd.

Created a fuzzer for l2cap classic internal dynamic channel allocator to
test DynamicChannelAllocator::IsPsmUsed(Psm psm).

Bug: 142684649
Test: bluetooth_gd_fuzz_test
Change-Id: If7c66d6aefc5d52448824f7f96f3118607a37215