docs: Recommend Debian 11 & fix Python CHIP Controller how-to

[agners]

Problem

• Debian 10 fails with

  Setting up Python environment.....[|]============================================================
Unexpected Python version: Python 3.7.3

• Following docs/guides/python_chip_controller_building.md venv source out/python_env/bin/activate doesn't exist

Change overview

• Recommend Debian 11. Debian 10 brings Python 3.7 which isn't supported anymore.
• Use -i separate to setup venv for Python CHIP Controller

Testing

[CLAassistant]

All committers have signed the CLA.

[github-actions]

PR #17938: Size comparison from df644b2 to c936ccb

Full report (23 builds for cc13x2_26x2, cyw30739, efr32, k32w, linux, mbed, nrfconnect, p6, telink)

platform	target	config	section	df644b2	c936ccb	change	% change
cc13x2_26x2	all-clusters-app	LP_CC2652R7	(read only)	688879	688879	0	0.0
			(read/write)	163376	163376	0	0.0
			.bss	75236	75236	0	0.0
			.data	3400	3400	0	0.0
			.rodata	102303	102303	0	0.0
			.text	586092	586092	0	0.0
	lock-ftd	LP_CC2652R7	(read only)	676735	676735	0	0.0
			(read/write)	166776	166776	0	0.0
			.bss	73548	73548	0	0.0
			.data	3224	3224	0	0.0
			.rodata	94359	94359	0	0.0
			.text	581896	581896	0	0.0
	lock-mtd	LP_CC2652R7	(read only)	625487	625487	0	0.0
			(read/write)	146352	146352	0	0.0
			.bss	69268	69268	0	0.0
			.data	3224	3224	0	0.0
			.rodata	94247	94247	0	0.0
			.text	530752	530752	0	0.0
	pump-app	LP_CC2652R7	(read only)	661227	661227	0	0.0
			(read/write)	183524	183524	0	0.0
			.bss	73764	73764	0	0.0
			.data	3256	3256	0	0.0
			.rodata	80387	80387	0	0.0
			.text	580356	580356	0	0.0
	pump-controller-app	LP_CC2652R7	(read only)	654123	654123	0	0.0
			(read/write)	190428	190428	0	0.0
			.bss	73820	73820	0	0.0
			.data	3220	3220	0	0.0
			.rodata	83323	83323	0	0.0
			.text	570316	570316	0	0.0
cyw30739	light	cyw930739m2evb_01	(read/write)	626322	626322	0	0.0
			.app_xip_area	528856	528856	0	0.0
			.bss	80116	80116	0	0.0
			.data	696	696	0	0.0
			.rodata	0	0	0	0.0
			.text	0	0	0	0.0
	lock	cyw930739m2evb_01	(read/write)	625026	625026	0	0.0
			.app_xip_area	529024	529024	0	0.0
			.bss	78692	78692	0	0.0
			.data	660	660	0	0.0
			.rodata	0	0	0	0.0
			.text	0	0	0	0.0
	ota-requestor-no-progress-logging	cyw930739m2evb_01	(read/write)	574170	574170	0	0.0
			.app_xip_area	468548	468548	0	0.0
			.bss	88016	88016	0	0.0
			.data	572	572	0	0.0
			.rodata	0	0	0	0.0
			.text	112	112	0	0.0
efr32	lighting-app	BRD4161A	(read only)	908168	908168	0	0.0
			(read/write)	135128	135128	0	0.0
			.bss	133072	133072	0	0.0
			.data	2052	2052	0	0.0
			.text	908160	908160	0	0.0
		BRD4161A+rpc	(read only)	942512	942512	0	0.0
			(read/write)	151808	151808	0	0.0
			.bss	149552	149552	0	0.0
			.data	2256	2256	0	0.0
			.text	942504	942504	0	0.0
		BRD4161A+rs911x	(read only)	746468	746468	0	0.0
			(read/write)	129352	129352	0	0.0
			.bss	127372	127372	0	0.0
			.data	1980	1980	0	0.0
			.text	746460	746460	0	0.0
	lock-app	BRD4161A+wf200	(read only)	916480	916480	0	0.0
			(read/write)	127540	127540	0	0.0
			.bss	125604	125604	0	0.0
			.data	1936	1936	0	0.0
			.text	916472	916472	0	0.0
	window-app	BRD4161A	(read only)	845416	845416	0	0.0
			(read/write)	133216	133216	0	0.0
			.bss	131248	131248	0	0.0
			.data	1964	1964	0	0.0
			.text	845408	845408	0	0.0
k32w	light	k32w061+release	(read/write)	684204	684204	0	0.0
			.bss	81320	81320	0	0.0
			.data	2008	2008	0	0.0
			.text	599172	599172	0	0.0
	lock	k32w061+release	(read/write)	729100	729100	0	0.0
			.bss	81744	81744	0	0.0
			.data	1968	1968	0	0.0
			.text	643684	643684	0	0.0
linux	chip-tool-no-interactive-ipv6only	arm64	(read only)	8692244	8692244	0	0.0
			(read/write)	616305	616305	0	0.0
			.bss	40913	40913	0	0.0
			.data	1192	1192	0	0.0
			.data.rel.ro	555648	555648	0	0.0
			.dynamic	560	560	0	0.0
			.got	14736	14736	0	0.0
			.init	24	24	0	0.0
			.init_array	184	184	0	0.0
			.rodata	429748	429748	0	0.0
			.text	6865252	6865252	0	0.0
	thermostat-no-ble	arm64	(read only)	2360948	2360948	0	0.0
			(read/write)	174593	174593	0	0.0
			.bss	86273	86273	0	0.0
			.data	1496	1496	0	0.0
			.data.rel.ro	79048	79048	0	0.0
			.dynamic	560	560	0	0.0
			.got	4736	4736	0	0.0
			.init	24	24	0	0.0
			.init_array	376	376	0	0.0
			.rodata	145748	145748	0	0.0
			.text	1986048	1986048	0	0.0
mbed	lock-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2418140	2418140	0	0.0
			.bss	205884	205884	0	0.0
			.data	5856	5856	0	0.0
			.text	1380740	1380740	0	0.0
nrfconnect	all-clusters-app	nrf52840dk_nrf52840	(read/write)	1180075	1180075	0	0.0
			bss	142000	142000	0	0.0
			rodata	150804	150804	0	0.0
			text	808588	808588	0	0.0
p6	all-clusters-app	default	(read/write)	2528512	2528512	0	0.0
			.bss	139256	139256	0	0.0
			.data	2792	2792	0	0.0
			.text	1486776	1486776	0	0.0
	light-app	default	(read/write)	2419112	2419112	0	0.0
			.bss	132720	132720	0	0.0
			.data	2592	2592	0	0.0
			.text	1377376	1377376	0	0.0
	lock-app	default	(read/write)	2428384	2428384	0	0.0
			.bss	132544	132544	0	0.0
			.data	2552	2552	0	0.0
			.text	1386648	1386648	0	0.0
telink	lighting-app	tlsr9518adk80d	(read/write)	807324	807324	0	0.0
			bss	75432	75432	0	0.0
			noinit	40416	40416	0	0.0
			text	571118	571118	0	0.0