feat: upgrade to Polkadot v0.9.26

[wischli]

fixes KILTProtocol/ticket#2101

• Upgrades to latest Polkadot v0.9.26
• No database or runtime migrations required

Noteworthy mentions

• [S] ✅ audited Add Event to Pallet Transaction Payment paritytech/substrate#11618 Low - Add event to pallet transaction payment
• [P] ✅ trivial Allow relay chain council to send XCMs paritytech/polkadot#5597 ❗️ Medium - Allow relay chain council to send xcms
• [S] ✅ audited Democracy.fast_track not allowed with zero voting period paritytech/substrate#11666 ❗️ Medium - Democracy.fast_track not allowed with zero voting period
• [S] ✅ trivial Pump the gossip engine while waiting for the BEEFY runtime pallet (memory leak fix) paritytech/substrate#11694 ❗️ Medium - Pump the gossip engine while waiting for the beefy runtime pallet (memory leak fix)

Checklist:

• I have verified that the code works
  • No panics! (checked arithmetic ops, no indexing array[3] use get(3), ...)
• I have verified that the code is easy to understand
• I have left the code in a better state
• I have documented the changes (where applicable)

[wischli]

Interesting to note: For standalone we do a lazy assignment of the TransactionPayment module:

TransactionPayment: pallet_transaction_payment = 7,

For the parachain runtimes we don't. That's why we did not have to add the Event<T> type as was done for Spiritnet and Peregrine.

[ntn-x2]

LGTM!

[weichweich]

LGTM!