feat(config): support for setting default visibility_mode via config

[zwang28]

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What's changed and what's your intention?

Previously the default value of visibility_mode session var is hard coded. It's inconvenient for a user who wants a different visibility_mode, because it need be set per session. And usually user always use the same visibility_mode for the same cluster.

This PR adds support for setting default visibility_mode for all sessions from a frontend node via its config.

• For a new session, visibility_mode session var is Default, which is interpreted as reading from config.
• If visibility_mode session var is set (All or Checkpoint), it overrides config one.

#8940

Checklist For Contributors

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have demonstrated that backward compatibility is not broken by breaking changes and created issues to track deprecated features to be removed in the future. (Please refer to the issue)
• All checks passed in ./risedev check (or alias, ./risedev c)

Checklist For Reviewers

• I have requested macro/micro-benchmarks as this PR can affect performance substantially, and the results are shown.

Documentation

• My PR DOES NOT contain user-facing changes.

Click here for Documentation

Types of user-facing changes

Please keep the types that apply to your changes, and remove the others.

• Installation and deployment
• Connector (sources & sinks)
• SQL commands, functions, and operators
• RisingWave cluster configuration changes
• Other (please specify in the release note below)

Release note

[codecov]

Codecov Report

Merging #10186 (85b6822) into main (0cd063f) will decrease coverage by 0.01%.
The diff coverage is 74.35%.

@@            Coverage Diff             @@
##             main   #10186      +/-   ##
==========================================
- Coverage   70.82%   70.82%   -0.01%     
==========================================
  Files        1234     1234              
  Lines      211336   211355      +19     
==========================================
+ Hits       149675   149682       +7     
- Misses      61661    61673      +12     

Flag	Coverage Δ
rust	70.82% <74.35%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
src/frontend/src/handler/query.rs	27.24% <0.00%> (ø)
src/frontend/src/lib.rs	19.04% <ø> (ø)
...frontend/src/scheduler/hummock_snapshot_manager.rs	65.80% <66.66%> (ø)
src/frontend/src/session.rs	27.62% <66.66%> (+0.31%)	⬆️
src/frontend/src/scheduler/worker_node_manager.rs	68.83% <71.42%> (-0.05%)	⬇️
src/common/src/session_config/visibility_mode.rs	80.00% <85.71%> (+0.83%)	⬆️
src/common/src/config.rs	82.28% <100.00%> (+0.16%)	⬆️
src/common/src/session_config/mod.rs	33.49% <100.00%> (ø)
src/frontend/src/handler/explain.rs	69.23% <100.00%> (ø)
src/meta/src/manager/cluster.rs	73.21% <100.00%> (-0.19%)	⬇️

... and 5 files with indirect coverage changes

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