Predefine Vector Capacity for LogRecord Attributes

[lalitb]

Fixes #1896

Please provide a brief description of the changes here.

Merge requirement checklist

• [x] CONTRIBUTING guidelines followed
• [ ] Unit tests added/updated (if applicable)
• [ ] Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• [x] Changes in public API reviewed (if applicable)