Implement gzip compression for HTTP client

[srikanthccv]

Part of #112

[codecov[bot]]

Codecov Report

Merging #125 (35ca046) into main (1993a38) will decrease coverage by 0.36%. The diff coverage is 65.21%.

@@            Coverage Diff             @@
##             main     #125      +/-   ##
==========================================
- Coverage   75.49%   75.13%   -0.37%     
==========================================
  Files          23       23              
  Lines        1706     1725      +19     
==========================================
+ Hits         1288     1296       +8     
- Misses        313      322       +9     
- Partials      105      107       +2     

Impacted Files	Coverage Δ
client/internal/httpsender.go	70.51% <60.00%> (-1.75%)	:arrow_down:
client/httpclient.go	94.73% <100.00%> (ø)
client/internal/tcpproxy.go	76.19% <0.00%> (-4.77%)	:arrow_down:

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[tigrannajaryan]

@srikanthccv thanks for the PR. Can you please implement the server-side gzip support first? Ideally we want to merge that first before merging this PR, otherwise someone may try to enable client-side compression and it won't work because server doesn't support it yet.

[srikanthccv]

@tigrannajaryan PTAL https://github.com/open-telemetry/opamp-go/pull/126