Docs/sangshuduo/td 10469 blm3 (#8299)

* [TD-10469]<docs>: use blm3 for devops

* update techdoc to include telegraf/collectd/statsd

* resolve conflict.

* [TD-10469]<docs>: use blm3 for devops

* resolve conflict.

* update tech doc.

also change go proxy to cn

* [TD-10469]<docs>: use blm3 for devops

* resolve conflict.

* fix collectd and statsd section

* [TD-10469]<docs>: use blm3 for devops

* resolve conflict.

* fix conflicts.

* [TD-10469]<docs>: use blm3 for devops

* resolve conflict.

* update doc for blm3's change

* fix faq port list

* add cmake to pick up blm3 or httpd options.

README.md

@@ -129,6 +129,17 @@ mkdir debug && cd debug
 cmake .. && cmake --build .
 ```
 
+Note TDengine 2.3.0.0 and later use a component named 'blm3' to play http daemon role by default instead of the http daemon embedded in the early version of TDengine. The blm3 is programmed by go language. If you pull TDengine source code to the latest from an existing codebase, please execute 'git submodule update --init --recursive' to pull blm3 source code. Please install go language 1.14 or above for compiling blm3. If you meet difficulties regarding 'go mod', especially you are from China, you can use a proxy to solve the problem.
+```
+go env -w GO111MODULE=on
+go env -w GOPROXY=https://goproxy.cn,direct
+```
+
+Or you can use the following command to choose to embed old httpd too.
+```
+cmake .. -DBUILD_HTTP=true
+```
+
 You can use Jemalloc as memory allocator instead of glibc:
 ```
 apt install autoconf