IsoManager: Add state dump

Adds state dump in the following format:
  ----------------
   ISO Manager:
    Available credits: 16
    Controller buffer size: 960
    CISes:
    BISes:
      BIS Connection handle: 130
        BIG Handle: 0
        Used Credits: 0
        SDU Interval: 10000
        State Flags: 0x14
      BIS Connection handle: 131
        BIG Handle: 0
        Used Credits: 0
        SDU Interval: 10000
        State Flags: 0x14
  ----------------

Bug: 150670922
Tag: #feature
Test: build, flash,  run `adb shell dumpsys bluetooth_manager` and verify the output
Sponsor: jpawlowski@
Change-Id: I2a0fde14d132ec2e3db4800939e0b6aa5ecdab7e