[Bug]: Stackdriver exporter fails to build with tonic certificate error when updating to 0.21

[msdrigg]

What happened?

When updating from 0.20 to 0.21, I am seeing this error

Error: Logging failed to set up

Caused by:
    0: Failed to init stackdriver exporter
    1: tonic error: transport error
    2: transport error
    3: invalid peer certificate: UnknownIssuer
    4: invalid peer certificate: UnknownIssuer

This is caused by this line in StackDriverExporter::Builder::build

opentelemetry-rust-contrib/opentelemetry-stackdriver/src/lib.rs

Line 188 in 9cd566b

.map_err(|e| Error::Transport(e.into()))?;

I believe the problem is that tonic 0.12 now requires explicitly setting use_webpki_roots() or use_native_roots() in ClientTlsConfig, and does not implicitly default to enabling them if not enabled (See this PR here hyperium/tonic#1731)

So the fix would be to make sure ClientTlsConfig explicitly calls .use_webpki_roots() or .use_native_roots() in all places that they are created (depending on enabled features.

API Version

Crate version 0.20

SDK Version

Crate version 0.24

What component are you working with?

opentelemetry-stackdriver

Relevant log output

Error: Logging failed to set up

Caused by:
    0: Failed to init stackdriver exporter
    1: tonic error: transport error
    2: transport error
    3: invalid peer certificate: UnknownIssuer
    4: invalid peer certificate: UnknownIssuer