[porteer] charge fees that the sovereign account has to pay on all hops

[clangenb]

See discussion: integritee-network/parachain#325 (comment)

Reasons for changing fees:

• unbalances DEXes on AHs (better to balance DEXes)
• global change of exchange rates among relevant tokens TEER, KSM, DOT
• runtime upgrades changing weights
• upstream configuration changes (bridge relayer fee)

In any case, it is very likely that multihop fees need to be changeds at the same time, so we can extend XcmFeeConfig with a field local