Channel: Fix channel state max and add regression test

[ddustin]

Twice now that I've been aware of the channel state max wasn't updated and it slipped through without being noticed.

This PR adds an explicit test so CI will fail if the max value isn't updated.

[ksedgwic]

We could add a sentinel as the explicit last state so we wouldn't have to update the CHANNEL_STATE_MAX expr every time ...

	CHANNELD_AWAITING_SPLICE,
	DUALOPEND_OPEN_COMMIT_READY,

	/* Always keep this one last */
	CHANNEL_STATE_LIMIT
};
#define CHANNEL_STATE_MAX  (CHANNEL_STATE_LIMIT - 1)

[Lagrang3]

Nit:

I tested this.
If I add a new channel state type, eg FUTURE_CHANNEL_STATE, I must also update
many switch statements through the code or the compiler complains about a state not being handled, like for example:

./wallet/wallet.h: In function ‘channel_state_in_db’:
./wallet/wallet.h:232:9: error: enumeration value ‘FUTURE_CHANNEL_STATE’ not handled in switch [-Werror=switch]

Once all of those compiler errors are resolved the test ./common/test/run-channel_type doesn't fail.
One would need the compiler to force the user to put the new channel state value in common/test/run-channel_type.c as well
to make this test fail correctly. By removing the default case.

[Lagrang3]

Suggested change

	bool known_state;
	switch(state) {
	case DUALOPEND_OPEN_INIT:
	case CHANNELD_AWAITING_LOCKIN:
	case CHANNELD_NORMAL:
	case CHANNELD_SHUTTING_DOWN:
	case CLOSINGD_SIGEXCHANGE:
	case CLOSINGD_COMPLETE:
	case AWAITING_UNILATERAL:
	case FUNDING_SPEND_SEEN:
	case ONCHAIN:
	case CLOSED:
	case DUALOPEND_OPEN_COMMITTED:
	case DUALOPEND_AWAITING_LOCKIN:
	case CHANNELD_AWAITING_SPLICE:
	case DUALOPEND_OPEN_COMMIT_READY:
	largest_state = state;
	known_state = true;
	break;
	default:
	known_state = false;
	break;
	bool known_state = false;
	switch(state) {
	case DUALOPEND_OPEN_INIT:
	case CHANNELD_AWAITING_LOCKIN:
	case CHANNELD_NORMAL:
	case CHANNELD_SHUTTING_DOWN:
	case CLOSINGD_SIGEXCHANGE:
	case CLOSINGD_COMPLETE:
	case AWAITING_UNILATERAL:
	case FUNDING_SPEND_SEEN:
	case ONCHAIN:
	case CLOSED:
	case DUALOPEND_OPEN_COMMITTED:
	case DUALOPEND_AWAITING_LOCKIN:
	case CHANNELD_AWAITING_SPLICE:
	case DUALOPEND_OPEN_COMMIT_READY:
	largest_state = state;
	known_state = true;
	break;

[ddustin]

Ah yes you are absolutely correct! Nice find.