Changed to: "In the above sample, `print_result` is used to simplify the printing of the result set. It is similar to `taos_use_result`"

Stylistic changes.
Clarifying changes.
Removed reference to taos_use_result since it is not mentioned in code snippet.

Grammar updates to Data Subscription page.

* docs: add subscribe demo for c

* docs: add subscribe demo for c

* docs: add R example source code

* test: check if RJDBC was installed

* test: add R test scripts

* test: chmod of test_R.sh

* test: fix test_go.sh; add R sample to document

* test: add test scripts to cases.task

* test: fix errors caused by  tset_python.sh and test_java.sh

* test: fix  test_python.sh

* test: modify java test case and improve opentsdb-json.mdx

* test: fix test_R.sh

* add c examples and subscribe examples files for other languages

* add query example

* c sample code

* c query example

* insert - create files

* refine slug

* create sample files for query

* add note

* [TD-13408]<test>: move examples back

* [TD-13408]<test>: move examples back

* add examples/c to CMakeLists.txt

* update tests

* [TD-13408]<test>: move rust example back

* fix examples path for Windows

* fix tests/exmaples

[TD-13005] <doc> del alert doc