Everywhere: Use to_number<T> instead of to_{int,uint,float,double}

In a bunch of cases, this actually ends up simplifying the code as
to_number will handle something such as:

```
Optional<I> opt;
if constexpr (IsSigned<I>)
    opt = view.to_int<I>();
else
    opt = view.to_uint<I>();
```

For us.

The main goal here however is to have a single generic number conversion
API between all of the String classes.

Userland/Libraries/LibC/grp.cpp

@@ -88,7 +88,7 @@ static bool parse_grpdb_entry(char* buffer, size_t buffer_size, struct group& gr
     auto& gid_string = parts[2];
     StringView members_string = parts[3];
 
-    auto gid = gid_string.to_uint();
+    auto gid = gid_string.to_number<gid_t>();
     if (!gid.has_value()) {
         warnln("parse_grpdb_entry(): Malformed GID on line {}", s_line_number);
         return false;

Userland/Libraries/LibC/netdb.cpp

@@ -767,7 +767,7 @@ static bool fill_getproto_buffers(char const* line, ssize_t read)
     }
     __getproto_name_buffer = split_line[0];
 
-    auto number = split_line[1].to_int();
+    auto number = split_line[1].to_number<int>();
     if (!number.has_value())
         return false;
 

Userland/Libraries/LibC/pwd.cpp

@@ -88,12 +88,12 @@ static bool parse_pwddb_entry(char* raw_line, struct passwd& passwd_entry)
     auto& dir = parts[5];
     auto& shell = parts[6];
 
-    auto uid = uid_string.to_uint();
+    auto uid = uid_string.to_number<uid_t>();
     if (!uid.has_value()) {
         dbgln("getpwent(): Malformed UID on line {}", s_line_number);
         return false;
     }
-    auto gid = gid_string.to_uint();
+    auto gid = gid_string.to_number<gid_t>();
     if (!gid.has_value()) {
         dbgln("getpwent(): Malformed GID on line {}", s_line_number);
         return false;

Userland/Libraries/LibC/scanf.cpp

@@ -410,7 +410,7 @@ extern "C" int vsscanf(char const* input, char const* format, va_list ap)
         [[maybe_unused]] int width_specifier = 0;
         if (format_lexer.next_is(isdigit)) {
             auto width_digits = format_lexer.consume_while([](char c) { return isdigit(c); });
-            width_specifier = width_digits.to_int().value();
+            width_specifier = width_digits.to_number<int>().value();
             // FIXME: Actually use width specifier
         }
 

Userland/Libraries/LibC/shadow.cpp

@@ -79,7 +79,7 @@ static bool parse_shadow_entry(ByteString const& line)
     auto& expire_string = parts[7];
     auto& flag_string = parts[8];
 
-    auto lstchg = lstchg_string.to_int();
+    auto lstchg = lstchg_string.to_number<int>();
     if (!lstchg.has_value()) {
         dbgln("getspent(): Malformed lstchg on line {}", s_line_number);
         return false;
@@ -87,7 +87,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (min_string.is_empty())
         min_string = "-1"sv;
-    auto min_value = min_string.to_int();
+    auto min_value = min_string.to_number<int>();
     if (!min_value.has_value()) {
         dbgln("getspent(): Malformed min value on line {}", s_line_number);
         return false;
@@ -95,7 +95,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (max_string.is_empty())
         max_string = "-1"sv;
-    auto max_value = max_string.to_int();
+    auto max_value = max_string.to_number<int>();
     if (!max_value.has_value()) {
         dbgln("getspent(): Malformed max value on line {}", s_line_number);
         return false;
@@ -103,7 +103,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (warn_string.is_empty())
         warn_string = "-1"sv;
-    auto warn = warn_string.to_int();
+    auto warn = warn_string.to_number<int>();
     if (!warn.has_value()) {
         dbgln("getspent(): Malformed warn on line {}", s_line_number);
         return false;
@@ -111,7 +111,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (inact_string.is_empty())
         inact_string = "-1"sv;
-    auto inact = inact_string.to_int();
+    auto inact = inact_string.to_number<int>();
     if (!inact.has_value()) {
         dbgln("getspent(): Malformed inact on line {}", s_line_number);
         return false;
@@ -119,7 +119,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (expire_string.is_empty())
         expire_string = "-1"sv;
-    auto expire = expire_string.to_int();
+    auto expire = expire_string.to_number<int>();
     if (!expire.has_value()) {
         dbgln("getspent(): Malformed expire on line {}", s_line_number);
         return false;
@@ -127,7 +127,7 @@ static bool parse_shadow_entry(ByteString const& line)
 
     if (flag_string.is_empty())
         flag_string = "0"sv;
-    auto flag = flag_string.to_int();
+    auto flag = flag_string.to_number<int>();
     if (!flag.has_value()) {
         dbgln("getspent(): Malformed flag on line {}", s_line_number);
         return false;