Don't impl HttpClient for reqwest::blocking::Client on wasm32

[OliverEvans96]

Fixes #1472

Changes

reqwest::blocking is not implemented on wasm32. Currently, the opentelemetry-http crate contains impl HttpClient for reqwest::blocking::Client, which prevents it from compiling on WASM. This PR conditionally removes that impl.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: OliverEvans96 / name: Oliver Evans (5efe944)
• ✅ login: lalitb / name: Lalit Kumar Bhasin (70bd531, b049138)

[TommyCpp]

reqwest::blocking is not implemented on wasm32

Could you link the source or any doc for this?

[lalitb]

Weird that the test are failing for this PR, and not others:

running 1 test
test build_tonic ... FAILED

failures:

---- build_tonic stdout ----
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/common/v1/common.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/resource/v1/resource.proto
error: test failed, to rerun pass `-p opentelemetry-proto --test grpc_build`
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/trace/v1/trace.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/collector/trace/v1/trace_service.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/metrics/v1/metrics.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/collector/metrics/v1/metrics_service.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/logs/v1/logs.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto/opentelemetry/proto/collector/logs/v1/logs_service.proto
cargo::rerun-if-changed=src/proto/tracez.proto
cargo::rerun-if-changed=src/proto/opentelemetry-proto
cargo::rerun-if-changed=src/proto
thread 'build_tonic' panicked at opentelemetry-proto/tests/grpc_build.rs:161:9:
generated file has changed but it's a CI environment, please rerun this test locally and commit the changes
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[OliverEvans96]

reqwest::blocking is not implemented on wasm32

Could you link the source or any doc for this?

https://github.com/seanmonstar/reqwest/blob/cc3dd510c0cb50ee03be217ea864d84e744658d1/src/lib.rs#L370-L377

Note that the wasm directory has no blocking.rs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.3%. Comparing base (ff9d50b) to head (70bd531).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2073   +/-   ##
=====================================
  Coverage   78.3%   78.3%           
=====================================
  Files        121     121           
  Lines      20815   20815           
=====================================
  Hits       16309   16309           
  Misses      4506    4506           

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