[nrfconnect] speed up BLE configuration

[LuDuda]

Problem

nRF connect platform default configuration uses small ATT_MTU and phy packet length.

Change overview

Adjust Bluetooth parameters to achieve better performance in commissioning and DFU over BLE. Related to #10177

Testing

Tested manually with Python CHIP Controller and Android CHIP Tool vs nRF52840 and nRF5340.

[github-actions]

Size increase report for "nrfconnect-example-build" from 257d179

File	Section	File	VM
chip-lock.elf	noinit	0	2970
chip-lock.elf	bss	0	192
chip-lock.elf	device_handles	8	8
chip-lock.elf	text	8	8
chip-shell.elf	noinit	0	2970
chip-shell.elf	bss	0	192
chip-shell.elf	text	8	8
chip-shell.elf	device_handles	-8	-8

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

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

sections,vmsize,filesize
noinit,2970,0
bss,192,0
.debug_line,0,12
device_handles,8,8
text,8,8
.debug_info,0,-8
.debug_loc,0,-60

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

sections,vmsize,filesize
noinit,2970,0
bss,192,0
.debug_line,0,8
text,8,8
.debug_info,0,-8
device_handles,-8,-8
.debug_loc,0,-64