The gRPC exporter does not respect timeout settings

[spadger]

Describe your environment

PHP 8.4, linux (in docker), php-fpm model
grpc module version => 1.69.0
latest version of transport-grpc

Steps to reproduce
There are 2 scenarios:

Scenario 1 (long timeout)

1. Set the following env vars:

OTEL_EXPORTER_OTLP_PROTOCOL: grpc
OTEL_EXPORTER_OTLP_ENDPOINT: http://google.com:4310
OTEL_EXPORTER_OTLP_TIMEOUT: 20000

2. export a batch of spans
3. observe the time for the request to complete

Expected: Request completes after 10 seconds
Actual: timeout completes after about 6 seconds

Scenario 2: short timeout (under 1 second)

1. Set the following env vars:

OTEL_EXPORTER_OTLP_PROTOCOL: grpc
OTEL_EXPORTER_OTLP_ENDPOINT: http://google.com:4310
OTEL_EXPORTER_OTLP_TIMEOUT: 999

2. export a batch of spans
3. observe the time for the request to complete

Expected: Request completes after about a second
Actual: Request completes immediately because the gRPC call immediately fails in less than 1ms (this also happens when you specify a valid collector endpoint and a 999ms timeout)