feat: add timestamp to log entries

[LayZeeDK]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

1. Timestamps are created at the time of writing the log to the drivers rather than when the log entry was created.
2. No timestamp property on LumberjackLog.
3. Timestamp is created non-deterministically.
4. Log factory functions are exposed.

Issue Number: N/A

What is the new behavior?

1. • A timestamp property on the log entry represents when it was created
2. • A createdAt: number property is added to LumberjackLog.
3. • A LumberjackTimeService is used to determine the timestamp and its formatter.
4. • Log factory functions are removed.

Does this PR introduce a breaking change?

[x] Yes
[ ] No

Log creators are removed, LumberjackLog#createdAt is added.

Other information

[LayZeeDK]

Let me know if we should use a different property name for LumberjackLog#timestamp. Maybe one of:

1. epochTicks
2. unitTimestamp
3. unixTicks
4. unixEpochTicks
5. unixEpochMilliseconds
6. epochMilliseconds
7. createdAt
8. createdAtTimestamp

[NachoVazquez]

Let me know if we should use a different property name for LumberjackLog#timestamp. Maybe one of:

I would go for 7 or 8. We could annotate it to describe how to handle the value but the name should be more meaningful.

[LayZeeDK]

Wait for updated CI #34.