Fix #1397, Rename overloaded EVS_PacketID_t to EVS_EventContext_t

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

• Fixes Overloaded "PacketID" use in CFE_EVS_PacketID #1397
  • Renames overloaded (and confusing) CFE_EVS_PacketID_t type to CFE_EVS_EventContext_t

Testing performed
GitHub CI actions all passing successfully (incl. Build + Run, Unit/Functional Tests etc.).

Expected behavior changes
No change to behavior.

Contributor Info
Avi Weiss @thnkslprpt

[jphickey]

In general I prefer the name "context" but this changes a public API. Some existing apps are referring to the PacketID name so it requires more discussion as to whether we really want to change it. For example the "HS" app is using PacketID, so this breaks HS. At a minimum this would need to go through the deprecation process (but I'm not sure if a simple name change warrants that, if nothing was actually broken)