feat(core): allow to overwrite default write API HTTP path

[sranka]

This PR allows changing the default HTTP path of InfluxDB write API service so that any endpoint that accepts InfluxDB line protocol data can be used:

  const writeAPI = new InfluxDB({url, token}).getWriteApi(org, bucket, precision)
  writeAPI.httpPath = '/api/v1/influxdb/write'

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• yarn test completes successfully
• Commit messages are conventional

[codecov-commenter]

Codecov Report

Merging #449 (42f42dc) into master (7a69f83) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #449   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           33        33           
  Lines         1234      1234           
  Branches       292       292           
=========================================
  Hits          1234      1234           

Impacted Files	Coverage Δ
packages/core/src/impl/WriteApiImpl.ts	100.00% <100.00%> (ø)

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[bednar]

LGTM 👍