Use updated fast_float::parse_options

Summary:
X-link: facebookincubator/zstrong#1216

`str_to_floating_fast_float_from_chars` can be simplified using the new upstream option `allow_leading_plus`. It does mean that we also support parsing `+nan` and `+infinity` which we previously didn't.

Mapping to `Inf` is also handled by the parsing logic, so this custom branch can be removed.

Reviewed By: Gownta

Differential Revision: D70392258

fbshipit-source-id: 62972a6cadd1547d8ff0a3162510ae5e979d459f

Author: javache

build/fbcode_builder/manifests/fast_float

@@ -2,12 +2,12 @@
 name = fast_float
 
 [download]
-url = https://github.com/fastfloat/fast_float/archive/refs/tags/v6.1.4.tar.gz
-sha256 = 12cb6d250824160ca16bcb9d51f0ca7693d0d10cb444f34f1093bc02acfce704
+url = https://github.com/fastfloat/fast_float/archive/refs/tags/v8.0.0.tar.gz
+sha256 = f312f2dc34c61e665f4b132c0307d6f70ad9420185fa831911bc24408acf625d
 
 [build]
 builder = cmake
-subdir = fast_float-6.1.4
+subdir = fast_float-8.0.0
 
 [cmake.defines]
 FASTFLOAT_TEST = OFF