[BUG] salt-ssh does not merge master top returns per saltenv

[lkubb]

Description
When multiple master top modules are defined and return targeted states for the same environment, salt-ssh does not merge the returns, but only keeps the last one. This is a discrepancy vs. regular Salt.

Setup
Enable two master top modules which return states for the same saltenv, e.g. base in the master config.

Steps to Reproduce the behavior
Check the output of salt-ssh foobar state.show_top.

Expected behavior
Lists should be merged, as usual.

Screenshots

salt/salt/client/ssh/state.py

Lines 107 to 111 in 93b6405

	for fun in self.tops:
	if fun not in self.opts.get("master_tops", {}):
	continue
	try:
	ret.update(self.tops[fun](opts=self.opts, grains=grains))

salt/salt/daemons/masterapi.py

Lines 533 to 539 in 93b6405

	for fun in self.tops:
	if fun not in self.opts.get("master_tops", {}):
	continue
	try:
	ret = salt.utils.dictupdate.merge(
	ret, self.tops[fun](opts=opts, grains=grains), merge_lists=True
	)

Versions Report
current master

Additional context
I just stumbled over this while writing a PR for #65479. Thought it was noteworthy enough.

Tangentially related: #59802