feat(agent):Agent supports conversation context

[yhjun1026]

Description

Closes #2219
Closes #2206

Agent supports conversation context historical message.

How Has This Been Tested?

Use directly in Agent application conversations.

Modify the following env configuration properties to adjust the range：

The agent historical message retention configuration defaults to the last two rounds.

MESSAGES_KEEP_START_ROUNDS=0
MESSAGES_KEEP_END_ROUNDS=2

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

[Aries-ckt]

r+

[fangyinc]

r+