Avoid to hold a strong reference to Context object

We only use parts of Context in the Content Capture manager and
main session, we don't need to cache context object which will
cause some memory issues.

This change will extract the necessary information to save it, instead
of caching the entire context object.

Bug: 256247718
Fixes: 239192932
Test: atest CtsContentCaptureServiceTestCases
Change-Id: Id7b5e8617c521f31879199b0f2c7e18204bb7526