fix: backslash escaping in serialization to Line protocol

[bednar]

Closes #302

Proposed Changes

The backslash does not have to be escaped in Measurement, Tag key, Tag value and Field key. For more info see:

https://docs.influxdata.com/influxdb/cloud/reference/syntax/line-protocol/#special-characters

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• pytest tests completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #303 (24b0b0d) into master (cf21862) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #303   +/-   ##
=======================================
  Coverage   92.64%   92.64%           
=======================================
  Files          27       27           
  Lines        2189     2189           
=======================================
  Hits         2028     2028           
  Misses        161      161           

Impacted Files	Coverage Δ
influxdb_client/client/write/point.py	99.18% <ø> (ø)

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