Add bazel build for grpc example

[lalitb]

grpc example ( https://github.com/open-telemetry/opentelemetry-cpp/tree/main/examples/grpc ) supports only cmake build as of now. bazel build needs to be added.

cc @jsuereth added bug as discussed here : #729 (review)

[owent]

I'm interesting in this. There some problems in #666 before.

• The old gRPC do not support legacy compilers and bazel 4.
• There are also more problems if using C++20 (Which remove many deprecated APIs before) even we use the gRPC with the version is not that old.

I'm not familiar with bazel and I think there may be the same problems if we add bazel support for grpc example.
Looking for the solution of best pratice.

[lalitb]

For the gcc compiler, we can document the minimum supported gcc version for gRPC/otlp as defined by gRPC (4.9+ or 5.1+ whatever works) :
gRPC needs gcc 4.9+(https://grpc.io/docs/), and abseil needs gcc 5.1+ (https://abseil.io/docs/cpp/platforms/platforms).

We can further split our Bazeil build CI into two parts - 4.8 compiler without building grpc/otlp, 5.1+ compiler with grpc/otlp. This will allow us to upgrade Bazel and gRPC versions both.

If all are fine, I can create a PR for updating our docs, and splitting Bazel build.

[lalitb]

I am putting it as help needed, probably someone with good knowledge bazel can help here.

[github-actions]

This issue was marked as stale due to lack of activity. It will be closed in 7 days.

[lalitb]

#910 fixes it.