Move agentcore memory properties which are used for the short-term memory only into extra space

[Vadym79]

Please move agentcore memory properties which are used for the short-term memory only, like

agentcore.memory.total-events-limit=10
agentcore.memory.default-session=default-session-id-12345678
agentcore.memory.page-size=50

and other into extra space, for example:

agentcore.memory.short-term.total-events-limit=10
agentcore.memory.short-term.default-session=default-session-id-12345678
agentcore.memory.short-term.page-size=50

With this, the naming will be concise and correspond how the agentcore memory long-term properties only are named.

[maschnetwork]

@ybezsonov can you take a look at this?