Delete RendezvousSession, and move code to controller and server

[pan-apple]

Problem

RendezvousSession class functionality can be consumed by DeviceCommissioner, and RendezvousServer classes. The current logic doesn't have a lot of overlap, and will save on code size and complexity by this refactor.

Summary of Changes

Move code to DeviceCommissioner, and RendezvousServer and delete RendezvousSession.

[github-actions]

Size increase report for "nrfconnect-example-build" from 237cfd0

File	Section	File	VM
chip-lighting.elf	device_handles	-8	-8
chip-lighting.elf	[LOAD #3 [RW]]	0	-23
chip-lighting.elf	bss	0	-169
chip-lighting.elf	rodata	-312	-316
chip-lighting.elf	text	-1096	-1096
chip-lock.elf	[LOAD #3 [RW]]	0	-8
chip-lock.elf	device_handles	-8	-8
chip-lock.elf	bss	0	-184
chip-lock.elf	rodata	-312	-312
chip-lock.elf	text	-1096	-1096

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-lighting.elf and ./pull_artifact/chip-lighting.elf:

sections,vmsize,filesize
.shstrtab,0,1
device_handles,-8,-8
[LOAD #3 [RW]],-23,0
bss,-169,0
.debug_aranges,0,-248
rodata,-316,-312
.debug_ranges,0,-440
.debug_frame,0,-648
text,-1096,-1096
.symtab,0,-1328
.debug_loc,0,-2305
.strtab,0,-2397
.debug_str,0,-2747
.debug_abbrev,0,-4743
.debug_line,0,-6052
.debug_info,0,-86985

Comparing ./master_artifact/chip-lock.elf and ./pull_artifact/chip-lock.elf:

sections,vmsize,filesize
.shstrtab,0,1
[LOAD #3 [RW]],-8,0
device_handles,-8,-8
bss,-184,0
.debug_aranges,0,-248
rodata,-312,-312
.debug_ranges,0,-440
.debug_frame,0,-648
text,-1096,-1096
.symtab,0,-1328
.debug_loc,0,-2293
.strtab,0,-2397
.debug_str,0,-2747
.debug_abbrev,0,-4396
.debug_line,0,-5861
.debug_info,0,-49143

[woody-apple]

@mspang @saurabhst ?