Hotfix/sangshuduo/td 5872 taosdemo stmt improve for master (#8015)

* cherry pick from develop branch.

* cherry pick 54813175

* [TD-5872]<fix>: taosdemo stmt csv perf improve.

* rand func back to early impl.

* fix windows/mac compile error.

* cherry pick from develop branch.

* merge with develop branch.

* rename MAX_SAMPLES_ONCE_FROM_FILE to reflect reality.

* split func for stmt interlace.

* fix bug that get build path.

* stmt batch interlace works.

* fix start time issue.

* few cleanup.

* fix nchar random length.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

src/kit/taosdemo/taosdemo.c

@@ -6388,7 +6388,7 @@ static int generateSampleFromRand(
 
                 case TSDB_DATA_TYPE_NCHAR:
                     dataLen = (columns)?columns[c].dataLen:g_args.binwidth;
-                    rand_string(data, dataLen);
+                    rand_string(data, dataLen - 1);
                     pos += sprintf(buff + pos, "%s,", data);
                     break;