Rename 'HttpTextFormat' to 'TextMapPropagator'

[malafeev]

fix #1581

[codecov]

Codecov Report

Merging #1586 into master will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #1586      +/-   ##
============================================
+ Coverage     91.62%   91.67%   +0.05%     
  Complexity      979      979              
============================================
  Files           116      116              
  Lines          3533     3533              
  Branches        307      307              
============================================
+ Hits           3237     3239       +2     
+ Misses          204      203       -1     
+ Partials         92       91       -1     

Impacted Files	Coverage Δ	Complexity Δ
.../src/main/java/io/opentelemetry/OpenTelemetry.java	98.21% <100.00%> (ø)	22.00 <0.00> (ø)
...ntelemetry/trace/propagation/HttpTraceContext.java	95.78% <100.00%> (ø)	25.00 <1.00> (ø)
...y/sdk/metrics/aggregator/DoubleMinMaxSumCount.java	100.00% <0.00%> (+3.92%)	6.00% <0.00%> (ø%)

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[jkwatson]

Can you add an entry to the "Unreleased" section of the CHANGELOG for this, since it's a breaking API change? Thanks!

[malafeev]

@jkwatson added entry to changelog

[anuraaga]

Thanks!