`initGlobalVariableIfNotExists` function forget close `rs`

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tidb/pkg/session/bootstrap.go

Lines 1043 to 1058 in c597cb5

	func initGlobalVariableIfNotExists(s sessiontypes.Session, name string, val any) {
	ctx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnBootstrap)
	rs, err := s.ExecuteInternal(ctx, "SELECT VARIABLE_VALUE FROM %n.%n WHERE VARIABLE_NAME=%?;",
	mysql.SystemDB, mysql.GlobalVariablesTable, name)
	terror.MustNil(err)
	req := rs.NewChunk(nil)
	err = rs.Next(ctx, req)
	terror.MustNil(err)
	if req.NumRows() != 0 {
	return
	}
	mustExecute(s, "INSERT HIGH_PRIORITY IGNORE INTO %n.%n VALUES (%?, %?);",
	mysql.SystemDB, mysql.GlobalVariablesTable, name, val)
	}

2. What did you expect to see? (Required)

call rs.Close before return

3. What did you see instead (Required)

forget call it and caused some states of s to not be cleaned up.

If mysql.GLOBAL_VARIABLES has a clustered index, it will report an error log like

[2025/06/20 16:07:36.838 +08:00] [FATAL] [bootstrap.go:3591] ["mustExecute error"] [error="try to commit with invalid txnStartTS: 18446744073709551615"] [stack="github.com/pingcap/tidb/pkg/session.mustExecute\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3591\ngithub.com/pingcap/tidb/pkg/session.initGlobalVariableIfNotExists\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3327\ngithub.com/pingcap/tidb/pkg/session.upgradeToVer209\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3181\ngithub.com/pingcap/tidb/pkg/session.upgrade\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:1556\ngithub.com/pingcap/tidb/pkg/session.runInBootstrapSession\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3732\ngithub.com/pingcap/tidb/pkg/session.bootstrapSessionImpl\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3458\ngithub.com/pingcap/tidb/pkg/session.BootstrapSession\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3404\nmain.createStoreDDLOwnerMgrAndDomain\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/cmd/tidb-server/main.go:416\nmain.main\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/cmd/tidb-server/main.go:320\nruntime.main\n\t/Users/pingcap/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.6.darwin-arm64/src/runtime/proc.go:272"] [stack="github.com/pingcap/tidb/pkg/session.mustExecute\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3591\ngithub.com/pingcap/tidb/pkg/session.initGlobalVariableIfNotExists\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3327\ngithub.com/pingcap/tidb/pkg/session.upgradeToVer209\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:3181\ngithub.com/pingcap/tidb/pkg/session.upgrade\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/bootstrap.go:1556\ngithub.com/pingcap/tidb/pkg/session.runInBootstrapSession\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3732\ngithub.com/pingcap/tidb/pkg/session.bootstrapSessionImpl\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3458\ngithub.com/pingcap/tidb/pkg/session.BootstrapSession\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/pkg/session/session.go:3404\nmain.createStoreDDLOwnerMgrAndDomain\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/cmd/tidb-server/main.go:416\nmain.main\n\t/Users/pingcap/workspace/bp-tidb-release-darwin-arm64-w2tsl-build-binaries/source/tidb/cmd/tidb-server/main.go:320\nruntime.main\n\t/Users/pingcap/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.6.darwin-arm64/src/runtime/proc.go:272"]

4. What is your TiDB version? (Required)

v8.5.2, master