[vm/ffi] Remove deprecated methods before D26

[dcharkes]

Before we ship D26, we should remove deprecated methods from the dart:ffi API:

• [vm/ffi] API: Pointer load and store as extension methods #37773 load and store (replaced by .val, .val=, .ref, [], and []=)
• [vm/ffi] Remove memory management from API #38520 allocate and free (moved to package:ffi)
• [vm/ffi] API: Pointer.asExternalTypedData as extension method #38610 asExternalTypedData (replaced by asTypedList extension method)

In order to be able to deprecate these at all in the sdk, we need to update the packages that are pulled in by DEPS (package:ffi and package:tflite_native).

We might also want to think about fixing g3.

cc @mkustermann @sjindel-google

[vsmenon]

If this is D26, can someone take ownership?

[sjindel-google]

I believe Daco is already working on this.

[mkustermann]

The main cl/121422 is up and reviewed. Removing the deprecated methods depends on that one.

It's blocked on getting our github mirror working again atm.

We'll try to use github directly in the mean time to bypass this broken mirror issue.

[dcharkes]

https://dart-review.googlesource.com/c/sdk/+/121708 CL ready, but blocked by CL addressing #38611.