Resolve merge conflicts with devel branch refactoring (#25423)

The PR branch had merge conflicts with `devel` due to a major compiler
refactoring that extracted type definitions from `compiler/ast.nim` into
a new `compiler/astdef.nim` file.

## Changes

- Resolved conflict in `compiler/ast.nim` by accepting `devel`'s
refactored structure
- Merged 763 commits from `devel` branch (commit range:
`ce6a345..b3273e7`)
- Preserved original PR changes removing deprecated symbols from
`lib/core/macros.nim`

The core PR functionality (removal of deprecated macros API since
v0.18.1) remains intact while incorporating the upstream AST
refactoring.

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tests/system/tconcat.nim

@@ -1,11 +1,33 @@
 discard """
-  output: "DabcD"
+  targets: "c cpp js"
+  output: '''
+DabcD
+(8192, 8, 1024)
+'''
 """
 
-const
-  x = "abc"
+import std/assertions
 
-var v = "D" & x & "D"
+block:
+  const
+    x = "abc"
 
-echo v
+  var v = "D" & x & "D"
 
+  doAssert v == "DabcD"
+  echo v
+
+block: # test large additions
+  var a = "abcdefgh"
+  let initialLen = a.len
+  let times = 10
+  for i in 1..times:
+    let start = a.len
+    a.add(a)
+    doAssert a.len == 2 * start
+  let multiplier = 1 shl times
+  doAssert a.len == initialLen * multiplier
+  echo (a.len, initialLen, multiplier)
+  for i in 1 ..< multiplier:
+    for j in 0 ..< initialLen:
+      doAssert a[j] == a[i * initialLen + j]