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
Merged-In: Id7b5e8617c521f31879199b0f2c7e18204bb7526
(cherry picked from commit c3380c16)