[analysis_server] use single function per type for canParse

Fixes #49229

Change-Id: I87d2dea79f8786b826162d132a63c69a2ebaba67
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/248009
Reviewed-by: Danny Tuppeny <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: asashour