Align joiner functionality on ncs example with other platforms

[ktaborowski]

Problem

Example lock-app for the nrfconnect platform does not support Thread Joiner role.

Summary of Changes

Add a Thread Joiner to an example. The Joiner is activated by pressing button 3 on nRF52 DK board.
New behavior is described in README file.

[CLAassistant]

All committers have signed the CLA.

[github-actions]

Size increase report for "gn_nrf-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

[github-actions]

Size increase report for "gn_linux-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

[github-actions]

Size increase report for "nrfconnect-example-build"

File	Section	File	VM
chip-nrf52840-lock-example.elf	text	3416	3416
chip-nrf52840-lock-example.elf	rodata	276	276
chip-nrf52840-lock-example.elf	bss	0	104
chip-nrf52840-lock-example.elf	[LOAD #1 [RWX]]	-8	-8
chip-nrf52840-lock-example.elf	[LOAD #3 [RW]]	0	-8

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-nrf52840-lock-example.elf and ./pull_artifact/chip-nrf52840-lock-example.elf:

sections,vmsize,filesize
.debug_info,0,601566
.debug_line,0,18192
.debug_loc,0,11991
.debug_abbrev,0,10638
.debug_str,0,5459
.strtab,0,3440
text,3416,3416
.symtab,0,2240
.debug_ranges,0,1776
.debug_frame,0,1236
.debug_aranges,0,424
rodata,276,276
bss,104,0
[Unmapped],0,-6
[LOAD #1 [RWX]],-8,-8
[LOAD #3 [RW]],-8,0

[github-actions]

Size increase report for "esp32-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-wifi-echo.elf and ./pull_artifact/chip-wifi-echo.elf:

sections,vmsize,filesize