Add required params to Builder constructors in Safety Center API.

Implements API council feedback (b/225891684) that asked us to add the
required title of SafetyCenterStaticEntry to the builder's
constructor. I have applied the same rule across the other builders in
the Safety Center API.

Updated JavaDocs accordingly, removing old "Required" notes.

Based on feedback and after understanding the process better I
reverted some non-essential tidying changes.

Fix: 225891684
Fix: 226628380
Test: CTS tests updated to use new builder constructors
CTS-Coverage-Bug: 225891684
Change-Id: I6c38fd1e139940c6964441bdee33f66b8f8267f9
Merged-In: I6c38fd1e139940c6964441bdee33f66b8f8267f9