Client: Refactor Asset Server functionality

[dhars9-roche]

• AssetServer now inherits from BaseServer — removed all duplicated get, put, post, parse, add_params, and url implementations.
• headers property on BaseServer (returns None by default) — subclasses override it to inject auth headers instead of overriding the HTTP methods.
• Fixed HTTP Warning header handling — old check_asset_warnings only triggered on status_code < 200 (wrong — those are informational codes). New _check_response_warnings checks on every response per RFC 7234, surfaces via UserLog().alert().
• Fixed warning suppression — replaced blanket with warnings.catch_warnings(record=True) (silently swallowed all warnings) with a targeted urllib3.InsecureRequestWarning filter when ssl_verify=False.
• parse() now raises IncorrectServerResponseError on bad JSON instead of a raw JSONDecodeError.

[dhars9-roche]

All Unit tests are passing fine.