floss: telephony: Support dialing operations from HF

Implemented the following functions and wired to btclient:
- SetMemoryCall
- SetLastCall

Added support of:
- Dialing a number from HF
- Dialing the last number from HF
- Dialing a number in the memory slot from HF

Bug: 214149380
Tag: #floss
Test: HFP/AG/OCM/BV-02-I, HFP/AG/OCL/BV-02-I
Change-Id: If109174a60fe13ebce0c6502ff5b33d516918ef6