fix(client): re-send session configuration on reconnect

[taka-2628]

Description

Session.initClusterConn() builds its TSOpenSessionReq without a Configuration map, while Session.Open() and Session.OpenCluster() both populate Configuration["sql_dialect"], ["version"], and ["db"]. Since reconnect() — the sole transparent-reconnect path, invoked from every insert/query/execute method on a transport error — routes exclusively through initClusterConn(), any session that reconnects after a server restart silently reverts to the server-default dialect with no database bound.

For table-model sessions this poisons the session: every subsequent statement is rejected with a SqlParseError (700) / SemanticError (701). Because these are valid server responses (*ExecutionError) rather than Go transport errors, TableSessionPool.isConnectionError returns false for them and the poisoned session is returned to the pool until the process restarts. The reference Java client re-sends this configuration on reconnect (SessionConnection.init() via reconnect()); the Go client did not.

Full analysis, including the diagnosis path and the pool-poisoning mechanism, in #177.

This bug exists because the same request-configuration block was hand-duplicated across three open paths and one copy was missed. This change extracts a single helper, buildOpenSessionConfiguration, and wires all three sites (Open, OpenCluster, initClusterConn) through it so they cannot drift again.

s.config already carries sqlDialect/Database at reconnect time. Cluster sessions carry no Version (ClusterConfig has no such field), so for them the empty-Version → DEFAULT_VERSION fallback reproduces exactly what OpenCluster() already sends.

Verification

• Reproduced and fixed against a live server. apache/iotdb:2.0.3-standalone with a TableSessionPool bound to a database: insert (succeeds) → docker restart the server → insert again on the reconnected pooled session. On the current code the post-restart insert fails with error code: 700 ... mismatched input 't' expecting ROOT (session reverted to tree dialect); with this change the post-restart insert succeeds. Same test, only the library changed.
• Added TestBuildOpenSessionConfiguration (table-driven, matching the existing session_test.go style). go build ./..., go vet ./client/, and go test ./client/ pass.

Out of scope (noted for maintainers)

initClusterConn also never sets s.timeFactor via getTimeFactor(resp), which Open/OpenCluster do — a reconnected session keeps a stale timeFactor. Benign on homogeneous clusters; happy to fold it into this PR if preferred.

Fixes #177