release: update CHANGELOG.md for v2.1.2 (tikv#1392)

Release v2.0.10 (tikv#1384)

Release v2.0.10 (tikv#1384)

Release v2.1.1 (tikv#1376)

* add v2.1.1 changelog

* Update CHANGELOG.md

Signed-off-by: disksing <[email protected]>

Co-Authored-By: disksing <[email protected]>

doc: add 2.1.0 changelog (tikv#1350)

add changelog for v2.0.9 (tikv#1332)

Signed-off-by: disksing <[email protected]>

Release v2.1.0-rc.5 (tikv#1322)

Signed-off-by: disksing <[email protected]>

*: release v2.1.0-rc.4 (tikv#1294)

Signed-off-by: disksing <[email protected]>

config: disable region merge (tikv#1259)