L2cap shim: Clean up LE dynamic channel part

Use cid token as a key for channels, just like what we did for classic,
to support multiple channels for the same PSM.

Also account for channel config and security policy.

Tag: #gd-refactor
Bug: 141555841
Test: cert/run --host
Test: CtsVerifier
Change-Id: Ia5a631e8603bbe51a2b53b1fe955e3f0c1e02325