Modify code comment for Worker build_id field #1160

[ntaylorkhan]

Solves #1160 by including language informing users that large codebase may result in long worker startup time when no build_id is given.

What was changed

worker doc comment for build_id field.

Why?

On initialization the best-effort process results in walking and MD5 hashing every module in the codebase, this is normally fast but in large codebases (15M+ lines of code) this can result in a long wait for worker to boot.

Users should have some way to know that providing build_id resolves this issue.

Checklist

1. Closes Modify code comment for Worker build_id field #1160

2. How was this tested:
   n/a

3. Any docs updates needed?
   n/a

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