Revert "Use SkSL "offset" to actually mean "line""

This reverts commit 47f76853c6266d02bfc914fe4e8160b60a1f903a.

Reason for revert: Test failures

Original change's description:
> Use SkSL "offset" to actually mean "line"
>
> SkSL internally tracks token offsets, but only ever reports errors using
> line numbers. With the introduction of the DSL, which (being embedded in
> C++ source) only has access to line numbers in the first place, tracking
> offsets went from merely providing little benefit to actively making
> life more difficult.
>
> We are changing SkSL's position tracking from handling offsets to
> handling line numbers, but to simplify the review process the change is
> split up into two main steps. The first step (this CL) starts using
> line numbers everywhere, but avoids the thousand-line churn of actually
> renaming "offset", so most "offset" fields, variables, and parameters
> will be briefly misnamed and will actually contain a line number.
>
> The followup CL will complete the process by renaming all of the
> now-misnamed fields, variables, and parameters, but will not make any
> behavioral changes.
>
> Bug: skia:12459
> Change-Id: I30dc87cf4b816c5ddd7b8ae1be32586388962085
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/451419
> Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> Reviewed-by: John Stiles <johnstiles@google.com>

Bug: skia:12459
Change-Id: I562d9980cd43a2fc5108e562155fe731a1761dca
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/452720
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
17 files changed