Regex should match both with and without a label

[dima-vm]

Describe the bug
Query metric_name{foo~="bar|"} doesn't return metrics with no label at all (notice | in regex)

To Reproduce

1. There is a metric that's scrapped both with and without a label, e.g.

metric_name 1.2345
metric_name{foo="bar"} 2.345
metric_name{foo="baz"} 3.456

2. Query metric_name{foo~="bar|"

Expected behavior
Should return:

metric_name
metric_name{foo="bar"}

but not

metric_name{foo="baz"}

[valyala]

Confirmed the bug. It will be fixed soon

[valyala]

The bug should be fixed in the following commits:

• single-node version - 318326c
• cluster version - d450249

These commits will be included into the next release.

[valyala]

The bugfix is available starting from v1.34.5