Client version metrics

Currently, sqld supports clients passing their client version via a x-libsql-client-version header. The value of this header should follow this pattern:

• Hrana/Remote clients should be libsql-remote-<language>-<version>
• Embedded replica clients should be libsql-rpc-<language>-<version>

<language> should be a reference to the language, for example, rust/go/js/python.

<version> should be a reference to either a semver version or a commit sha (first 6 chars of the sha).