Reland "Remove GrProgramDesc::KeyHeader structure"

This is a reland of 4bcd58afbf1a1993e453231c575b47a0ae1ec24d

Original change's description:
> Remove GrProgramDesc::KeyHeader structure
>
> Instead, just fold all of this information into the key, like everything
> else. The only value that was accessed elsewhere is the initial key
> length. That doesn't need to be part of the key, so store it separately
> in the GrProgramDesc.
>
> Removing this special case logic is just the first step in revising how
> we assemble keys.
>
> Bug: skia:11372
> Change-Id: I52eb76812045e1906797cb37e809cfd0b3332ef0
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376797
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

Bug: skia:11372
Change-Id: I2cdb49aee3537e54dad9af1f9b47cf1aed1aca21
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376849
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed