Update CLM to new spec requirements for attribute truncation

[MadScienceZone]

The Go agent reports all CLM data regardless of length. However, since generally speaking transaction attributes may be no longer than 255 characters, these attributes will end up getting truncated if, e.g., a function or path name is over that length. However, a truncated file or function name is useless for subsequent use by CLM since the true, full name is missing.

Instead, implement the following logic to handle any cases where the CLM attributes would be too long:

For any given trace:

• drop any CLM attribute if it's over 255 characters
• if code.function doesn't exist or if the function name is over 255 characters, drop all CLM attributes
• if code.function exists and both code.namespace and code.filepath are over 255 characters, drop all CLM attributes

[nr-swilloughby]

Sorry, I was signed in from my personal github account when I posted that issue :/