API to modify/remove an existing entry from LogRecord attributes

[lalitb]

Fixes #1986

Changes

This PR adds two new methods, update_attribute and delete_attribute, to the public API of the LogRecord struct.

pub fn update_attribute(&Key, &AnyValue) -> Option<AnyValue>

• Updates the value of the first occurrence of an attribute with the specified key.
• If the attribute already exists, its value is replaced, and the old value is returned.
• If the attribute is not found, it is added as a new key-value pair, and None is returned.

pub fn remove_attribute(&mut self, key: &Key) -> usize

• Removes all the occurrence of attributes with the specified key.
• The count of deleted attributes is returned .

Merge requirement checklist

• [x] CONTRIBUTING guidelines followed
• [x] 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)