tests: Bluetooth: BR: Add general test suite for SMP

IUT works as an SM Initiator/Responder. The peer device,
SM Responder/Initiator, is a PC running bumble on it.

Add shell commands to create and manage L2CAP server and channel with
different security level, reboot the board, and transfer data on the
SDP channel.

In the test suite, there are 28 test cases to verify SMP functions.
The test case list is:
- BR_SM_INIT_001: Basic Pairing with No Input No Output Capability
- BR_SM_INIT_002: Pairing with Display Only Capability
- BR_SM_INIT_003: Pairing with Keyboard Only Capability
- BR_SM_INIT_005: L2CAP Connection Failure After Successful Pairing
- BR_SM_INIT_006: L2CAP Server with Incoming Connection
- BR_SM_INIT_008: ACL Disconnection During Pairing
- BR_SM_INIT_011: Repeated Pairing Between Same Devices
- BR_SM_INIT_012: Security Level Escalation
- BR_SM_INIT_013: Multiple Channel Establishment
- BR_SM_INIT_017: Pairing Rejection by Remote Device
- BR_SM_INIT_018: Pairing Timeout
- BR_SM_INIT_021: Authentication Failure during Pairing
- BR_SM_INIT_022: Secure Connection vs. Legacy Pairing Fallback
- BR_SM_INIT_025: Rejection of Weak Pairing Methods
- BR_SM_INIT_028: Reconnection After Key Deletion
- BR_SM_INIT_029: Pairing with Delayed Response
- BR_SM_INIT_030: Stress Testing with Multiple Connect/Disconnect Cycles
- BR_SM_INIT_032: Power Loss Recovery
- BR_SM_INIT_034: Pairing During Active Data Transfer
- BR_SM_INIT_035: Pairing with Very Long PIN/Passkey
- BR_SM_INIT_037: Pairing with Peripheral Requesting Maximum Key Size
- BR_SM_INIT_039: Security Level Downgrade Attempt
- BR_SM_RSP_001: Basic Non-bondable Pairing with No Input No Output
- BR_SM_RSP_002: Display Only with Secure Connection
- BR_SM_RSP_003: Keyboard Only with Dedicated Bonding
- BR_SM_RSP_006: Security Level Enforcement
- BR_SM_RSP_008: L2CAP Connection with Security Level 1
- BR_SM_RSP_009: L2CAP Server with Security Level 2

Signed-off-by: Can Wang <can.wang@nxp.com>