[OpenThread] Optimize memory usage of DNS client

[Damian-Nordic]

Problem

In the worst-case scenario, the DNS client must correctly handle a commissionable node service which contains
a TXT entry with key "PI" and a pairing instruction up to 128 characters. Current DNS client implementation for OpenThread does not support such long TXT entries to limit the stack usage.

Change overview

Change the method of allocating memory for the resolved/discovered services to allow long TXT entries, yet not to consume too much memory on stack.
Fixes #8467.

Testing

Tested along with #8454 that nRF Connect Lock can both advertise and discover (with matter dns browse shell command) a node with the longest possible pairing instruction.

[github-actions]

Size increase report for "esp32-example-build" from 762a204

File	Section	File	VM
chip-lock-app.elf	.flash.text	64	64
chip-shell.elf	.flash.text	-32	-32
chip-temperature-measurement-app.elf	.flash.text	60	60

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

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

sections,vmsize,filesize
.debug_str,0,148
.debug_info,0,142
.flash.text,64,64
.debug_loc,0,-14
[Unmapped],0,-64

Comparing ./master_artifact/chip-ipv6only-app.elf and ./pull_artifact/chip-ipv6only-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

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

sections,vmsize,filesize
[Unmapped],0,32
.flash.text,-32,-32

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
.flash.text,60,60
.debug_info,0,59
.debug_str,0,16
.debug_loc,0,13
[Unmapped],0,-60

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_info,0,59
.debug_str,0,17
.riscv.attributes,0,-1
.debug_loc,0,-3

[github-actions]

Size increase report for "nrfconnect-example-build" from 762a204

File	Section	File	VM
chip-shell.elf	device_handles	8	8
chip-shell.elf	text	-56	-56
chip-lock.elf	device_handles	8	8
chip-lock.elf	text	-56	-56

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
.debug_info,0,317
.debug_loc,0,301
.debug_str,0,203
.debug_abbrev,0,36
.debug_line,0,35
.debug_ranges,0,16
device_handles,8,8
.debug_frame,0,-4
text,-56,-56

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

sections,vmsize,filesize
.debug_loc,0,305
.debug_str,0,203
.debug_info,0,188
.debug_line,0,40
.debug_abbrev,0,36
.debug_ranges,0,16
device_handles,8,8
.shstrtab,0,-1
.debug_frame,0,-4
.strtab,0,-11
text,-56,-56