std: Convert deprecated aliases to compile errors and fix usages

Deprecated aliases that are now compile errors:

- `std.fs.MAX_PATH_BYTES` (renamed to `std.fs.max_path_bytes`)
- `std.mem.tokenize` (split into `tokenizeAny`, `tokenizeSequence`, `tokenizeScalar`)
- `std.mem.split` (split into `splitSequence`, `splitAny`, `splitScalar`)
- `std.mem.splitBackwards` (split into `splitBackwardsSequence`, `splitBackwardsAny`, `splitBackwardsScalar`)
- `std.unicode`
  + `utf16leToUtf8Alloc`, `utf16leToUtf8AllocZ`, `utf16leToUtf8`, `fmtUtf16le` (all renamed to have capitalized `Le`)
  + `utf8ToUtf16LeWithNull` (renamed to `utf8ToUtf16LeAllocZ`)
- `std.zig.CrossTarget` (moved to `std.Target.Query`)

Deprecated `lib/std/std.zig` decls were deleted instead of made a `@compileError` because the `refAllDecls` in the test block would trigger the `@compileError`. The deleted top-level `std` namespaces are:

- `std.rand` (renamed to `std.Random`)
- `std.TailQueue` (renamed to `std.DoublyLinkedList`)
- `std.ChildProcess` (renamed/moved to `std.process.Child`)

This is not exhaustive. Deprecated aliases that I didn't touch:
  + `std.io.*`
  + `std.Build.*`
  + `std.builtin.Mode`
  + `std.zig.c_translation.CIntLiteralRadix`
  + anything in `src/`

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/std/Random.zig b/lib/std/Random.zig
index 681f70bc98..0ba048eb0c 100644
--- a/lib/std/Random.zig
+++ b/lib/std/Random.zig
@@ -9,7 +9,7 @@ const math = std.math;
 const mem = std.mem;
 const assert = std.debug.assert;
 const maxInt = std.math.maxInt;
-pub const Random = @This(); // Remove pub when `std.rand` namespace is removed.
+const Random = @This();
 
 /// Fast unbiased random numbers.
 pub const DefaultPrng = Xoshiro256;