Adding HTTP2 transport settings in util/httpclient

[julienstroheker]

Related to #395

This pull request introduces a new feature to enable HTTP2 client ping with configurable timeouts via environment variables. The changes include updates to the HTTP client initialization and the addition of new tests to ensure the feature works as expected.

Using the 3 following env variables :

HTTP2_TRANSPORT_PING_ENABLED           // bool
HTTP2_TRANSPORT_READ_IDLE_TIMEOUT      // time.Duration
HTTP2_TRANSPORT_PING_TIMEOUT           // time.Duration

HTTP Client Enhancements:

• Added support for HTTP2 client ping with configurable read idle timeout and ping timeout via environment variables in util/httpclient/utils.go.
• Modified the HTTP client initialization to set up HTTP2 ping if the corresponding environment variable is enabled.

Testing:

• Added comprehensive tests in util/httpclient/utils_test.go to verify the HTTP2 client ping functionality and default HTTP client properties.

[bcho]

LGTM

[weinong]

approved