[TRACKING]: Port new capabilities from CF's in-tree plugin framework

[araujof]

Description

This issue tracks PRs affecting the plugin framework that have been created in ContextForge since CPEX extraction.

PRs touching mcpgateway/plugins/framework/ (since #3639)

PR	State	Title	Files Changed
#4068	MERGED	Feature/plugin multi tenancy with per tool plugin config	__init__.py, manager.py, models.py
#4062	MERGED	feat: implement hierarchical plugin condition evaluation	utils.py
#4034	MERGED	fix: honor fail_on_plugin_error during plugin init	manager.py
#4005	MERGED	Fixes #3925: Implemented the content_types field functionality for PluginCondition	models.py, utils.py
#3983	OPEN	#3808 role-aware Cedar policy plugin with tool-level gating	hooks/http.py
#3933	OPEN	chore: remove flake8, darglint, dlint; replace with ruff D417	external/mcp/tls_utils.py
#3872	MERGED	feat(observability): add OTEL root and client spans for MCP flows	external/mcp/server/runtime.py, manager.py
#3814	MERGED	fix/3811-pipe-validation-issue	external/grpc/, external/unix/, loader/plugin.py, external/proto_convert.py
#3774	MERGED	feat: add retry-with-exponential-backoff plugin	manager.py, models.py
#3713	OPEN	feat(security): container image scanner plugin (Trivy/Grype)	__init__.py, hooks/gateway.py
#3658	OPEN	feat(security): container image scanner (earlier iteration)	__init__.py, hooks/gateway.py

cc: @jonpspri