feat:add test for operator encode/decode

Rephrasing and spelling

Rephrased sentences, some stylistic changes.

Stylistics, grammar and changed string "topic" to "topicname" in one Java example code snippet since topic is a keyword in TDengine.

fix: meta latest version

test: add test case for vector function such as csum  , mavg , diff 

test:add test case

fix(os): config remote server info

Test/gxy query 3.0.0

test: add schemaless-insert 1-insert/opentsdb_telnet_line_taosc_insert.py to CI

fix: avoid mem leak

Stylistic changes.

rephrased slightly

Spelling, grammar and stylistic.

for 3.0

[TD-15999]

feat:add encode/decode for operator

fix(os): length overflow error

refactor: mnode snapshot

fix(os): add one win case