fix: postgresql read schema_info with characters truncated if too long

[bigcash]

Description

当使用postgresql数据库时，当读取表的字段较多时，这时使用sqlalchemy读取后并转为字符串后，会出现中间部分字段被”characters truncated“现象。debug查看变量发现，所有字段是都在的，只不过在加入大模型的prompt模板时，自动的toString功能会自动进行truncated。改问题记录在 1426

How Has This Been Tested?

使用postgresql数据库，并设计一个超过30个字段的表，且每个字段名称的长度约大于10个字符。这时，如果在chat dashboard时，生成的prompt中会发现有中间部分的字段名称被”characters truncated“了。更新本代码后，问题解决。

Snapshots:

Include snapshots for easier review.

Checklist:

• My code follows the style guidelines of this project
• I have already rebased the commits and make the commit message conform to the project standard.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules

[csunny]

r+, thank for your contribution, and congratulations on being the 100th contributor.

[Aries-ckt]

r+