fix(prometheus): keep/drop patterns split on any whitespace, and a *_time_seconds value reads as a moment (#6423)

A pasted drop list whose line breaks had become spaces was stored as one
pattern that matched nothing, so Home Assistant's two 526-series
bookkeeping families filled the 1,000-series cap. No metric name holds
whitespace, so patterns now split on spaces and tabs as well as lines
and commas.

Home Assistant names its Unix times *_time_seconds (e.g.
homeassistant_last_updated_time_seconds), which read as "20751d 21h".
is_moment() takes both suffixes, for the value shown and the chart axis.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/plugins/prometheus/test_pages.py

@@ -72,6 +72,9 @@ def test_series_are_grouped_by_metric_with_their_labels_and_units():
         ("target=S", "fresh", ["fresh", "late"])]
     assert groups[2]["rows"][0]["resource"] == "A:target=S,state=fresh"
     assert shown_value("x_timestamp_seconds", 0) == {"text": "never", "moment": None}
+    # Home Assistant names its Unix times *_time_seconds (#6423): a moment, not "20751d 21h".
+    assert shown_value("homeassistant_last_updated_time_seconds", 1792964340.0) == {
+        "text": "", "moment": datetime.fromtimestamp(1792964340.0, timezone.utc)}
     assert shown_value("jobs_per_sec", 0.25)["text"] == "0.25/s"
     assert shown_value("job_seconds", 90)["text"] == "1m 30s"
     assert shown_value("anything", None)["text"] == "—"