internal/simdgen: use "NAME" for method names in doc strings

This will let us merge operations that differ only in their method
names. In particular, this will give us a robust way to insert
computed method names.

The YAML changes were done using the following Gemini CLI prompt:

  In all of the files named "categories.yaml", for each operation in
  the YAML list, find the Go method name from the "go" field, and
  replace anywhere that operation name appears as a word in the
  "documentation" field with the literal string "NAME". Please do this
  using Go with the yaml.v3 library. The yaml.v3 library is already
  imported in this module.

No effect on generated godefs.

Change-Id: Ifdac95c5d62475937fc33a8013d0b0c5c5dca312
Reviewed-on: https://go-review.googlesource.com/c/arch/+/691340
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Austin Clements <austin@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>