[nrf5] build with internal OpenThread

[bukepo]

Problem

On nRF52 platform, examples use the prebuilt OpenThread libraries. This is not makes it hard to land new OpenThread features or bug fixes in time.

Summary of Changes

Build OpenThread from source on nRF52 platform.

[CLAassistant]

All committers have signed the CLA.

[github-actions]

Size increase report for "nrf-example-build"

File	Section	File	VM
chip-nrf52840-lock-example.out	.text	193692	193692
chip-nrf52840-lock-example.out	.data	-32	-32
chip-nrf52840-lock-example.out	.bss	0	-4572

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

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

sections,vmsize,filesize
.text,193692,193692
.debug_loc,0,88741
.strtab,0,76213
.debug_info,0,45293
.symtab,0,15888
[Unmapped],0,2916
.data,-32,-32
.debug_macro,0,-272
.bss,-4572,0
.debug_abbrev,0,-8251
.debug_aranges,0,-24224
.debug_ranges,0,-29944
.debug_line,0,-48999
.debug_frame,0,-62024
.debug_str,0,-191229

[github-actions]

Size increase report for "linux-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-standalone-demo.out and ./pull_artifact/chip-standalone-demo.out:

sections,vmsize,filesize

[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

[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

[bukepo]

I signed.