beacon/light/api: fixed blsync update query

[zsfelfoldi]

This PR fixes what #30306 broke. Escaping the ? in the event sub query was fixed in that PR but it was still escaped in the updates request. This PR adds a URL params argument to httpGet and fixes updates query formatting.

[holiman]

Even after looking at this fix, and the previous fix, and playing with it in my IDE, I fail to spot the error. Please point it out to me...

[holiman]

Ok, I got an explanation now, I'll post it here for visibility. There's this method

func (api *BeaconLightApi) httpGet(path string) ([]byte, error) 

Which @s1na fixed to escape the path.
However, it's called by

func (api *BeaconLightApi) httpGetf(format string, params ...any) ([]byte, error) {
	return api.httpGet(fmt.Sprintf(format, params...))
}

called by

func (api *BeaconLightApi) GetBestUpdatesAndCommittees(firstPeriod, count uint64) ([]*types.LightClientUpdate, []*types.SerializedSyncCommittee, error) {
	resp, err := api.httpGetf("/eth/v1/beacon/light_client/updates?start_period=%d&count=%d", firstPeriod, count)

So, the httpGetf accepts params, but passes the full path + params as path to httpGet -- which now escapes the already escaped param-string.

So it's a semantic mixup, IMO the httpGetf must not use httpGet, because what it's passing is not path, but a full query.

[zsfelfoldi]

Now it's fixed in a nice way. httpGet makes a full query (which is required for updates) while httpGetf makes a request to a formatted string path with no additional query params (which is required for most of the other requests where parameters are actually a part of the path).

[holiman]

This httpGetf method is a bit useless, IMO. It's now used in three places, so they can write e.g

	resp, err := api.httpGetf("/eth/v1/beacon/headers/%s", blockId)

instead of

	resp, err := api.httpGet(fmt.Sprintf("/eth/v1/beacon/headers/%s", blockId))

I approve of this patch, but I also wouldn't mind dropping that method.

[zsfelfoldi]

I agree, httpGetf removed.