[cleanup] Clean up InstallFunction variants in the bootstrapper

- Remove an unused param from InstallFunction
- Remove an InstallFunction variant which just rearranges the order of
  the arguments
- Consistently use const char* string literals as property names rather
  than e.g. factory->return_string() just write "return" because it is
  easier for humans to read. All the strings are internalized anyway and
  this happens at mksnapshot time, so there is no performance penalty.
- Remove the maybe_prototype arguments to CreateFunction. We always know
  at the callsite whether we have a prototype or not, so just call the
  variant that takes a prototype or the new CreateFunction variant which
  takes a Builtin::name.
- Rename a SimpleInstallFunction variant which was only used for symbols
  to InstallFunctionAtSymbol. This also makes it clear that this is the
  only case where property_name and function_name differ.

Bug: v8:8238
Change-Id: I2400de90ebe837694e777cff1419858037ee51cc
Reviewed-on: https://chromium-review.googlesource.com/c/1349271Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57769}