fix: lots of corner cases in PromQL

[waynexia]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

Changes 😇

• don't generate filter plan if there is no filter
• don't include timestamp filter in filter plan
• fix how the offset is handled
• consider the stale NaN case
• don't filter NaN for instant selector
• ignore nonexistent time series in range selector

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

#1042

[codecov]

Codecov Report

Merging #1345 (4127cc1) into develop (da66138) will decrease coverage by 0.78%.
The diff coverage is 90.83%.

❗ Current head 4127cc1 differs from pull request most recent head 0d4e03a. Consider uploading reports for the commit 0d4e03a to get more accurate results

@@             Coverage Diff             @@
##           develop    #1345      +/-   ##
===========================================
- Coverage    85.84%   85.06%   -0.78%     
===========================================
  Files          506      514       +8     
  Lines        76861    77471     +610     
===========================================
- Hits         65980    65901      -79     
- Misses       10881    11570     +689     

[fengjiachun]

lgtm