Send event data over a map instead of a string for better data representation.

Introduced a new field called `params` which is a key-value pair of a string and a list of string fields mapping all necessary event associated data.

Bug: 250899887
Test: system/gd/cert/run --topshim --clean
Tag: #floss
Change-Id: I7b0443888e3677386a187eb5ff28b61c20d6fd5d