fix!: fix regression caused by unbalanced partitions and splitting ranges (#5090)

* feat: assign partition ranges by rows

* feat: balance partition rows

* feat: get uppoer bound for part nums

* feat: only split in non-compaction seq scan

* fix: parallel scan on multiple sources

* fix: can split check

* feat: scanner prepare by request

* feat: remove scan_parallelism

* docs: upate docs

* chore: update comment

* style: fix clippy

* feat: skip merge and dedup if there is only one source

* chore: Revert "feat: skip merge and dedup if there is only one source"

Since memtable won't do dedup jobs

This reverts commit 2fc7a54b11.

* test: avoid compaction in sqlness window sort test

* chore: do not create semaphore if num partitions is enough

* chore: more assertions

* chore: fix typo

* fix: compaction flag not set

* chore: address review comments

src/cmd/tests/load_config_test.rs

@@ -69,7 +69,6 @@ fn test_load_datanode_example_config() {
             region_engine: vec![
                 RegionEngineConfig::Mito(MitoConfig {
                     auto_flush_interval: Duration::from_secs(3600),
-                    scan_parallelism: 0,
                     experimental_write_cache_ttl: Some(Duration::from_secs(60 * 60 * 8)),
                     ..Default::default()
                 }),
@@ -205,7 +204,6 @@ fn test_load_standalone_example_config() {
                 RegionEngineConfig::Mito(MitoConfig {
                     auto_flush_interval: Duration::from_secs(3600),
                     experimental_write_cache_ttl: Some(Duration::from_secs(60 * 60 * 8)),
-                    scan_parallelism: 0,
                     ..Default::default()
                 }),
                 RegionEngineConfig::File(EngineConfig {}),