[librsvg] (45 commits) ...Merge branch 'observable-api' into 'main'

[Marge Bot <marge-bot src gnome org>]

Summary of changes:

  d839c73... New CairoContextState struct to capture the state of a pass
  83e2fc9... devel-docs/api-observability.md: Development docs for obser
  fe81d49... Desiderata for observability
  4a4351c... More details on the design doc for observability
  143b02f... Convert the observability doc to rst
  3c26699... CairoContextState: capture the initial matrix
  dc6b58d... session.rs: new file with a Session type, to track metadata
  d7af0a2... Loader: create a Session, even if it does not do anything y
  e0e9010... SvgHandle: turn into a real struct, from a tuple struct
  23dc7b1... SvgHandle: store a Session, too
  4231dc2... Handle: store a Session
  2e5b953... Session: move the fields to an inner Arc<T>
  e372e71... rsvg_log_session!(): new macro, uses a Session to decide wh
  eb1f738... Session.new_for_test_suite(): New method
  d0c3d5a... Pass a Session around the document loading code
  2f8c132... xml/mod.rs: Use a session for logging
  63731fd... DrawingCtx: use a session for logging
  156f1da... DrawingCtx: expose a session() method so it can be used aro
  05adeae... shapes.rs: Use a session for logging where we have a Drawin
  f08a55b... element.rs: Use the DrawingCtx.session()
  2c2f0d1... Pass a session to the PaintServer.resolve() functions
  aaaa42d... api.rs: mark the SvgHandle._session as an unused field
  99c0c09... paint_server.rs: Use rsvg_log_session! in a couple of place
  5341853... CairoContextState: suppress a warning until we use this for
  5300bb6... layout.rs: Use a session for logging
  63ee11c... filter.rs: Use the DrawingCtx's session for logging
  8919cf8... image.rs: Use a session for logging
  7e9b0df... filters/mod.rs: Use a session for logging
  f6be4ee... impl Default for Session
  0c0bbf5... c_api/handle.rs: Keep a Session for the CHandle and log to 
  ab21884... c_api: Pass a session to set_gerror
  ad2b1d3... css.rs: Use a session for logging
  c0a336b... Pass a Session to the node creation code
  03fa7ca... Pass a Session to the cascading machinery
  cca3638... Pass a Session to set_attributes() functions
  ed471ca... Pass a session to ElementInner.set_error()
  ae982ed... api.rs: Oops, don't re-export UserLanguage
  91deb9c... api.rs: Move the UserLanguage::new constructor to here
  f0c8de5... Pass a session to UserLanguage::new()
  a3799b3... Pass a Session to the gradient.resolve machinery
  b0559cb... ElementInner: remove the big result field, and substitute f
  8e74dab... Remove the rsvg_log macro now that it is unused
  3625293... Session: move the RSVG_LOG detection code to here
  8cf6b3a... Rename rsvg_log_session back to rsvg_log
  9aafae4... Merge branch 'observable-api' into 'main'