feat(linq): add support for Async queries

[bednar]

Closes #238

Proposed Changes

Added support for asynchronous queries for LINQ driver.

Checklist

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

[codecov-commenter]

Codecov Report

Merging #239 (99271e5) into master (09986be) will increase coverage by 0.16%.
The diff coverage is 84.21%.

@@            Coverage Diff             @@
##           master     #239      +/-   ##
==========================================
+ Coverage   85.11%   85.28%   +0.16%     
==========================================
  Files          71       71              
  Lines        6296     6366      +70     
==========================================
+ Hits         5359     5429      +70     
  Misses        937      937              

Impacted Files	Coverage Δ
Client.Linq/Internal/QueryExecutor.cs	89.85% <81.08%> (-10.15%)	⬇️
Client.Linq/InfluxDBQueryable.cs	91.42% <84.84%> (-5.87%)	⬇️
Client/QueryApi.cs	24.50% <100.00%> (+1.14%)	⬆️
Client.Core/Internal/AbstractQueryClient.cs	81.64% <0.00%> (+5.79%)	⬆️

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