Fix convert numbers to strings

[liuxiaocs7]

• SubTask of [Feature] 支持 JDBC 导入 DATE 数据类型, 并存在自动强制转化成文本问题 #298
• Close [Bug] The target data type must be number #299

fix data type transfer when number in database but declare as text(string) in schema.

eg:

29         ->     "29"
199.67     ->     "199.67"

result(metrics log):

>> HugeGraphLoader worked in NORMAL MODE
vertices/edges loaded this time : 8/0
--------------------------------------------------
count metrics
    input read success            : 8                   
    input read failure            : 0                   
    vertex parse success          : 8                   
    vertex parse failure          : 0                   
    vertex insert success         : 8                   
    vertex insert failure         : 0                   
    edge parse success            : 0                   
    edge parse failure            : 0                   
    edge insert success           : 0                   
    edge insert failure           : 0                   
--------------------------------------------------
meter metrics
    total time                    : 0.062s              
    read time                     : 0.036s              
    load time                     : 0.026s              
    vertex load time              : 0.026s              
    vertex load rate(vertices/s)  : 307                 
    edge load time                : 0s                  
    edge load rate(edges/s)       : -1   

Local UTs:

[codecov]

Codecov Report

Merging #465 (7b059ac) into master (44a0818) will decrease coverage by 0.01%.
The diff coverage is 40.00%.

@@             Coverage Diff              @@
##             master     #465      +/-   ##
============================================
- Coverage     62.51%   62.50%   -0.01%     
- Complexity      894     1868     +974     
============================================
  Files            91      260     +169     
  Lines          4396     9429    +5033     
  Branches        516      875     +359     
============================================
+ Hits           2748     5894    +3146     
- Misses         1445     3151    +1706     
- Partials        203      384     +181     

Impacted Files	Coverage Δ
.../apache/hugegraph/structure/constant/DataType.java	61.53% <0.00%> (ø)
...org/apache/hugegraph/loader/util/DataTypeUtil.java	70.13% <50.00%> (-0.79%)	⬇️

... and 168 files with indirect coverage changes

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[imbajin]

LGTM