gc: Added LFS3_GC_ALL to make running all gc work easier

This is an alias for all possible gc work, which is a bit more
complicated than you might think due to compile-time features (example:
LFS3_GC_REPOPGBMAP).

The intention is to make loops like the following easy to write:

  struct lfs3_fsinfo fsinfo;
  lfs3_fs_stat(&lfs3, &fsinfo) => 0;

  lfs3_trv_t trv;
  lfs3_trv_open(&lfs3, &trv, fsinfo.flags & LFS3_GC_ALL) => 0;
  ...

It's possible to do this by explicitly setting all gc flags, but that
requires quite a bit of knowledge from the user.

Another option is allowing -1 for gc/traversal flags, but that loses
assert protection against unknown/misplaced flags.

---

This raises more questions about the prefix naming: it feels a bit weird
to take LFS3_I_* flags, mask with LFS3_GC_* flags, and pass them as
LFS3_T_* flags, but it gets the job done.

Limiting LFS3_GC_ALL to the LFS3_GC_* namespace avoids issues with
opt-out/mode flags such as LFS3_T_RDONLY, LFS3_T_MTREEONLY, etc. For
this reason it probably doesn't make sense to add something similar to
the other namespaces.

lfs3.h

@@ -369,6 +369,16 @@ enum lfs3_btype {
 #define LFS3_GC_CKMETA  0x00001000  // Check metadata checksums
 #define LFS3_GC_CKDATA  0x00002000  // Check metadata + data checksums
 
+// an alias for all possible GC work
+#define LFS3_GC_ALL ( \
+        LFS3_IFDEF_RDONLY(0, LFS3_GC_MKCONSISTENT) \
+            | LFS3_IFDEF_RDONLY(0, LFS3_GC_REPOPLOOKAHEAD) \
+            | LFS3_IFDEF_RDONLY(0, \
+                LFS3_IFDEF_GBMAP(LFS3_GC_REPOPGBMAP, 0)) \
+            | LFS3_IFDEF_RDONLY(0, LFS3_GC_COMPACTMETA) \
+            | LFS3_GC_CKMETA \
+            | LFS3_GC_CKDATA)
+
 
 // Configuration provided during initialization of the littlefs
 struct lfs3_cfg {