video/out/gpu/context: convert --gpu-context to use obj_settings_list

Since the list of available GPU contexts is a compile time constant,
use obj_settings_list instead of opt_string_validate for GPU contexts.
This has several advantages:

- Aligns with the existing usage of vo, ao, and filter lists.
- Allows custom probing order.
- Allows list option suffixes. (--gpu-context-append, etc.)
- Allows autocomplete in console.lua.
- Uses the standard obj_settings_list help printing, so the custom
  help printing function is no longer needed.

This also deduplicates some context creation code for ra_ctx_create
and ra_ctx_create_by_name.

1 files changed, 1 insertions, 1 deletions

diff --git a/video/out/gpu/context.h b/video/out/gpu/context.h
index f7107c9a71..0b422384d8 100644
--- a/video/out/gpu/context.h
+++ b/video/out/gpu/context.h
@@ -10,7 +10,7 @@ struct ra_ctx_opts {
     bool want_alpha;      // create an alpha framebuffer if possible
     bool debug;           // enable debugging layers/callbacks etc.
     bool probing;        // the backend was auto-probed
-    char *context_name;  // filter by `ra_ctx_fns.name`
+    struct m_obj_settings *context_list; // list of `ra_ctx_fns.name` to probe
     char *context_type;  // filter by `ra_ctx_fns.type`
 };