omni-node: Adjust manual seal parameters

[skunert]

This PR will make omni-node dev-mode once again compatible with older runtimes.

The changes introduced in #6825 changed constraints that are enforced in the runtime. For normal chains this should work fine, since we have real parameters there, like relay chain slots and parachain slots.

For these manual seal parameters we need to respect the constraints, while faking all the parameters. This PR should fix manual seal in omni-node to work with runtime build before and after #6825 (I tested that).

In the future, we should look into improving the parameterization here, possibly by introducing proper aura pre-digests so that the parachain slot moves forward. This will require quite a bit of refactoring on the manual seal node side however. Issue: #7453

Also, the dev chain spec in parachain template is updated. This makes it work with stable2412-1 and master omni-node. Once the changes here are backported and in a release, all combinations will work again.

fixes #7341

[skunert]

/cmd prdoc --audience runtime_dev --bump patch

[paritytech-workflow-stopper]

All GitHub workflows were cancelled due to failure one of the required jobs.
Failed workflow url: https://github.com/paritytech/polkadot-sdk/actions/runs/13140999658
Failed job name: test-linux-stable

[paritytech-cmd-bot-polkadot-sdk]

Created backport PR for stable2407:

• [stable2407] Backport #7451 #7485 with remaining conflicts!

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-7451-to-stable2407
git worktree add --checkout .worktree/backport-7451-to-stable2407 backport-7451-to-stable2407
cd .worktree/backport-7451-to-stable2407
git reset --hard HEAD^
git cherry-pick -x 9c474d5452a855adc843785c71fc842f81eeed56
git push --force-with-lease

[paritytech-cmd-bot-polkadot-sdk]

Created backport PR for stable2409:

• [stable2409] Backport #7451 #7486 with remaining conflicts!

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-7451-to-stable2409
git worktree add --checkout .worktree/backport-7451-to-stable2409 backport-7451-to-stable2409
cd .worktree/backport-7451-to-stable2409
git reset --hard HEAD^
git cherry-pick -x 9c474d5452a855adc843785c71fc842f81eeed56
git push --force-with-lease

[paritytech-cmd-bot-polkadot-sdk]

Created backport PR for stable2412:

• [stable2412] Backport #7451 #7487 with remaining conflicts!

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-7451-to-stable2412
git worktree add --checkout .worktree/backport-7451-to-stable2412 backport-7451-to-stable2412
cd .worktree/backport-7451-to-stable2412
git reset --hard HEAD^
git cherry-pick -x 9c474d5452a855adc843785c71fc842f81eeed56
git push --force-with-lease