Port builtins/string to Rust

- Add test to verify piped string replace exit code

Ensure fields parsing error messages are the same.

Note: C++ relied upon the value of the parsed value even when `errno` was set,
that is defined behaviour we should not rely on, and cannot easilt be replicated from Rust.
Therefore the Rust version will change the following error behaviour from:

```shell
> string split --fields=a "" abc
string split: Invalid fields value 'a'
> string split --fields=1a "" abc
string split: 1a: invalid integer
```

To:

```shell
> string split --fields=a "" abc
string split: a: invalid integer
> string split --fields=1a "" abc
string split: 1a: invalid integer
```

tests/checks/abbr.fish

@@ -199,3 +199,8 @@ abbr --add --regex foo --function foo
 # CHECKERR: abbr --add: Name cannot be empty
 echo foo
 # CHECK: foo
+
+abbr --add regex_name --regex '(*UTF).*' bar
+# CHECKERR: abbr: Regular expression compile error: using UTF is disabled by the application
+# CHECKERR: abbr: (*UTF).*
+# CHECKERR: abbr:      ^

tests/checks/string.fish

@@ -45,9 +45,13 @@ string length -q ""; and echo not zero length; or echo zero length
 string pad foo
 # CHECK: foo
 
-string pad -r -w 7 -c - foo
+string pad -r -w 7 --chars - foo
 # CHECK: foo----
 
+# might overflow when converting sign
+string sub --start -9223372036854775808 abc
+# CHECK: abc
+
 string pad --width 7 -c '=' foo
 # CHECK: ====foo
 
@@ -175,6 +179,10 @@ string split "" abc
 # CHECK: b
 # CHECK: c
 
+string split --max 1 --right 12 "AB12CD"
+# CHECK: AB
+# CHECK: CD
+
 string split --fields=2 "" abc
 # CHECK: b
 
@@ -185,6 +193,39 @@ string split --fields=3,2 "" abc
 string split --fields=2,9 "" abc; or echo "exit 1"
 # CHECK: exit 1
 
+string split --fields=2-3-,9 "" a
+# CHECKERR: string split: 2-3-,9: invalid integer
+
+string split --fields=1-99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 "" abc
+# CHECKERR: string split: 1-99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999: invalid integer
+
+string split --fields=99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999-1 "" abc
+# CHECKERR: string split: 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999-1: invalid integer
+
+string split --fields=1--2 "" b
+# CHECKERR: string split: 1--2: invalid integer
+
+string split --fields=0 "" c
+# CHECKERR: string split: Invalid fields value '0'
+
+string split --fields=99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 "" abc
+# CHECKERR: string split: 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999: invalid integer
+
+string split --fields=1-0 "" d
+# CHECKERR: string split: Invalid range value for field '1-0'
+
+string split --fields=0-1 "" e
+# CHECKERR: string split: Invalid range value for field '0-1'
+
+string split --fields=-1 "" f
+# CHECKERR: string split: -1: invalid integer
+
+string split --fields=1a "" g
+# CHECKERR: string split: 1a: invalid integer
+
+string split --fields=a "" h
+# CHECKERR: string split: a: invalid integer
+
 string split --fields=1-3,5,9-7 "" 123456789
 # CHECK: 1
 # CHECK: 2
@@ -359,6 +400,14 @@ string replace -r "\s*newline\s*" "\n" "put a newline here"
 string replace -r -a "(\w)" "\$1\$1" ab
 # CHECK: aabb
 
+echo a | string replace b c -q
+or echo No replace fails
+# CHECK: No replace fails
+
+echo a | string replace -r b c -q
+or echo No replace regex fails
+# CHECK: No replace regex fails
+
 string replace --filter x X abc axc x def jkx
 or echo Unexpected exit status at line (status --current-line-number)
 # CHECK: aXc
@@ -468,6 +517,22 @@ string repeat -n 5 --max 4 123 '' 789
 # CHECK:
 # CHECK: 7897
 
+# FIXME: handle overflowing nicely
+# overflow behaviour depends on 32 vs 64 bit
+
+# count here is isize::MAX
+# we store what to print as usize, so this will overflow
+# but we limit it to less than whatever the overflow is
+# so this should be fine
+# string repeat -m1 -n 9223372036854775807 aa
+# DONTCHECK: a
+
+# count is here (i64::MAX + 1) / 2
+# we end up overflowing, and the result is 0
+# but this should work fine, as we limit it way before the overflow
+# string repeat -m1 -n 4611686018427387904 aaaa
+# DONTCHECK: a
+
 # Historical string repeat behavior is no newline if no output.
 echo -n before
 string repeat -n 5 ''
@@ -766,6 +831,18 @@ string match -qer asd asd
 echo $status
 # CHECK: 0
 
+# should not be able to enable UTF mode
+string match -r "(*UTF).*" "aaa"
+# CHECKERR: string match: Regular expression compile error: using UTF is disabled by the application
+# CHECKERR: string match: (*UTF).*
+# CHECKERR: string match:      ^
+
+string replace -r "(*UTF).*" "aaa"
+# CHECKERR: string replace: Regular expression compile error: using UTF is disabled by the application
+# CHECKERR: string replace: (*UTF).*
+# CHECKERR: string replace:      ^
+
+
 string match -eq asd asd
 echo $status
 # CHECK: 0
@@ -832,6 +909,12 @@ echo "foo1x foo2x foo3x" | string match -arg 'foo(\d)x'
 echo -n abc | string upper
 echo '<eol>'
 # CHECK: ABC<eol>
+
+# newline should not appear from nowhere when command does not split on newline
+echo -n abc | string collect
+echo '<eol>'
+# CHECK: abc<eol>
+
 printf \<
 printf my-password | string replace -ra . \*
 printf \>\n