ci: use ubuntu 2004 to build weekly

[sunng87]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

This patch fixes #893 by assigning our ubuntu 20.04 runners to release tasks. We also changed lto to thin to speed up binary building.

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)

[codecov]

Codecov Report

Merging #895 (3d8b8d3) into develop (6f5639f) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #895      +/-   ##
===========================================
+ Coverage    86.31%   86.33%   +0.01%     
===========================================
  Files          427      427              
  Lines        57260    57295      +35     
===========================================
+ Hits         49426    49466      +40     
+ Misses        7834     7829       -5     

Flag	Coverage Δ
rust	86.33% <ø> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/servers/src/shutdown.rs	80.95% <0.00%> (-9.53%)	⬇️
src/meta-srv/src/error.rs	94.76% <0.00%> (-1.14%)	⬇️
src/cmd/src/datanode.rs	77.48% <0.00%> (-0.75%)	⬇️
src/datanode/src/instance.rs	65.55% <0.00%> (-0.32%)	⬇️
src/datanode/src/mock.rs	100.00% <0.00%> (ø)
src/datanode/src/datanode.rs	58.92% <0.00%> (+0.74%)	⬆️
src/servers/src/opentsdb.rs	98.41% <0.00%> (+1.58%)	⬆️
src/common/substrait/src/df_logical.rs	78.77% <0.00%> (+1.75%)	⬆️
src/datanode/src/heartbeat.rs	85.96% <0.00%> (+4.35%)	⬆️
src/servers/src/error.rs	40.74% <0.00%> (+5.55%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[zyy17]

👍

[killme2008]

LGTM