feat: add explicit FLUSH PRIVILEGES to refresh role cache for query node

[camilesing]

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Summary

for #19013

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[chatgpt-codex-connector]

💡 Codex Review

databend/src/query/service/src/servers/flight/v1/actions/kill_query.rs

Lines 26 to 28 in d486a0b

	pub async fn kill_query(plan: KillPlan) -> Result<bool> {
	let session = create_session(Some(plan.tenant.as_str()))?;
	let version = GlobalConfig::version();

Flight action plans reference nonexistent tenant field

The flight handlers now call create_session(Some(plan.tenant.as_str())), but the plan types they accept (KillPlan, SetPriorityPlan, TruncateTablePlan) still do not define a tenant field (see planner/plans/kill.rs, planner/plans/set_priority.rs, planner/plans/ddl/table.rs). This makes the changed lines fail to compile, so the build will break and these flight actions cannot run until the plan structs or calls are corrected.

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