Properly use config schema for theme settings

Added patch to recent 8.x-3.x

Does this issue explain why I get notices like this?

logo.url	URL	uri	Yes			This value should be of the correct primitive type.	
logo.use_default	Use default	boolean	Yes	TRUE			
schemas	Undefined	undefined	No	<array>	missing schema	schemas' is not a supported key.	
table_responsive	Undefined	undefined	No	-1	missing schema	table_responsive' is not a supported key.	
cdn_provider	Undefined	undefined	No		missing schema	cdn_provider' is not a supported key.	
cdn_theme	Undefined	undefined	No		missing schema	cdn_theme' is not a supported key.	
cdn_cache_ttl_versions	Undefined	undefined	No	0	missing schema	cdn_cache_ttl_versions' is not a supported key.	
cdn_cache_ttl_themes	Undefined	undefined	No	0	missing schema	cdn_cache_ttl_themes' is not a supported key.	
cdn_cache_ttl_assets	Undefined	undefined	No	0	missing schema	cdn_cache_ttl_assets' is not a supported key.	
cdn_cache_ttl_library	Undefined	undefined	No	0	missing schema	cdn_cache_ttl_library' is not a supported key.	
reset	Undefined	undefined	No	Reset Broken Cache	missing schema	reset' is not a supported key.	
apply	Undefined	undefined	No	Apply	missing schema	apply' is not a supported key.	
reset_http_request_cache	Undefined	undefined	No		missing schema	reset_http_request_cache' is not a supported key.	
table	Undefined	undefined	No		missing schema	table' is not a supported key.	

@hatuhay When closing an issue with Won’t fix, please provide information. A simple switch to Close is not enough.

Opened MR, here is a static patch for composer if anyone needs it.
and the interdiff with #20.

PS: I know 3.x is now phasing out but I need those schema fixes, we are planning a BS5 migration.

@xmacinfo
There were over 200 tickets on versions 8.x-3.x and 7.x sited for months or years.
Just did a cleanup for all over 6 months last interaction expexcting that if any of this tickets were still alive someone was going to pick it up and make it live again, like in this case.
Just for the record, this is the only one at the moment alive again.

#20 discarded most settings from the previous patch #13, what happened there?
Updated MR and patch, according to patch #13 instead.

Some more fixes... I think it should be ok now.

We need langcode now that some configs are translatable.

Note: there is no hook_update so, in bootstrap.settings and subtheme settings:
- add langcode: en
- if present, delete reset_http_request_cache, table, apply, reset configs