feat(attributes): add default attributes

[MateuszKepczynskiSauce]

Add fields:

application.session: an uuid that will be the same for all reports in single application session. 

guid: unique machine identifier 

uname.sysname - name of the operating system

backtrace.agent - name of the go library (this is a constant value set to backtrace-go)

backtrace.version - version of the go library 

uname.version - version of the operating system

hostname - current hostname

cpu.arch - CPU arch

cpu.brand - CPU brand

application - current application name 

process.id  - current process id