fix(config): trim trailing slashes on intake urls

[shreyamalpani]

What does this PR do?

Trims trailing slashes from DD_URL, DD_DD_URL, and DD_APM_DD_URL and DD_LOGS_CONFIG_LOGS_DD_URL in ConfigBuilder::build() before they're used downstream. A trailing slash on DD_DD_URL/DD_URL caused DdDdUrl::new()/DdUrl::new() (from the dogstatsd crate) to reject the URL with a UrlPrefixError, causing the extension to panic and crash on startup. Also, previously, a trailing slash on DD_APM_DD_URL would produce a double slash in the resulting intake URL because the suffix /api/v0.2/traces is added to the path.

Motivation

Reported in SVLS-9373: setting DD_URL/DD_DD_URL/DD_APM_DD_URL with a trailing slash produced malformed intake URLs for consumers of this crate.

Describe how to test/QA your changes

Added unit tests covering trailing-slash inputs for each affected env var. All existing tests in datadog-agent-config continue to pass.

Also tested manually with a lambda function, no longer crashes on parsing an env var url with a trailing slash.

[Copilot]

Pull request overview

This PR hardens datadog-agent-config URL handling by trimming trailing slashes from configured intake URLs during ConfigBuilder::build(), preventing downstream URL parsing errors (notably UrlPrefixError from the dogstatsd crate) and avoiding double-slash paths when suffixes are appended.

Changes:

• Trim trailing slashes for dd_url and url during config build.
• Trim trailing slashes before normalizing logs and APM intake URLs.
• Add unit tests covering trailing-slash inputs for DD_LOGS_CONFIG_LOGS_DD_URL, DD_DD_URL, DD_URL, and DD_APM_DD_URL.