fix!: use the right precision

[fengjiachun]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

Use the right precision.

Before: The data written with Influxdb line protocol before was stored as type Millisecond, resulting in loss of precision.
After: The data written with influxes line protocol and OTLP protocol will be stored as type "Nanosecond"

Note that this is a breaking change because the data storage type has changed from Millisecond to Nanosecond. For existing tables, new writes will result in an error. One solution is to delete the data and re-import it.

Others:

1. Remove writer.rs and line_writer.rs since we do not need them any more(There were for column protocol)
2. Add more unit test

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[killme2008]

Don't forget comments for pub functions/structures.

[codecov]

Codecov Report

Attention: Patch coverage is 83.03030% with 28 lines in your changes are missing coverage. Please review.

Project coverage is 85.25%. Comparing base (e0b5f52) to head (d0f4f23).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3794      +/-   ##
==========================================
- Coverage   85.56%   85.25%   -0.32%     
==========================================
  Files         947      946       -1     
  Lines      161503   161142     -361     
==========================================
- Hits       138198   137384     -814     
- Misses      23305    23758     +453     

[killme2008]

LGTM