Lock values in documentation examples

[ShahanaFarooqui]

With autogenerate example script, we are able to generate all rpc example but their values are not locked. So running this script will always change the doc/schemas/lightning-*.json's examples section. Temporarily developers can use REGENERATE='methodname1, methodname2' in command to re-generate a specific commands list.

• Add all askrene examples (currently failing due to _ in the method name)
• Lock all changing values (like port, timestamp, txid, payment_hash etc.)
• Add CI action to auto generate all examples (it will add approx 5 more minutes in the CI execution)

Reference PR: #7457.

[ShahanaFarooqui]

We will not include askrene examples in this PR. These examples will be added once the RPCs are finalized and APIs are more stable.