classes/crate-fetch: Ensure crate fetcher is available

Reworks the crate fetcher class to have it install the fetcher at recipe
finalization so that it is always available before SRC_URI is expanded.
In addition, override the value of SRCPV to also install the fetcher
when SRCPV is expanded so that AUTOREV works.

[YOCTO #10867]

(From OE-Core rev: bc66c5dd65fb654af5cd91b47f9b4f7a5f53436e)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/crate-fetch.bbclass

@@ -7,7 +7,22 @@
 # crate://<packagename>/<version>
 #
 
-python () {
+def import_crate(d):
-        import crate
+    import crate
-        bb.fetch2.methods.append( crate.Crate() )
+    if not getattr(crate, 'imported', False):
+        bb.fetch2.methods.append(crate.Crate())
+        crate.imported = True
+
+python crate_import_handler() {
+    import_crate(d)
 }
+
+addhandler crate_import_handler
+crate_import_handler[eventmask] = "bb.event.RecipePreFinalise"
+
+def crate_get_srcrev(d):
+    import_crate(d)
+    return bb.fetch2.get_srcrev(d)
+
+# Override SRCPV to make sure it imports the fetcher first
+SRCPV = "${@crate_get_srcrev(d)}"