ARC Analysis in one pass v3 (#17068)

* Analyse last reads all at once

* Integrate firstWrite analysis

* Small cleanup

* Use sets instead of seqs

* Remove instrTargets

* Reap the benefits

* Implement error diagnostics

* Operate on DFA index for lastRead analysis

* Use mgetOrPut

* Cache alias results

This improves performance by a lot, since many
CFG locations map to a single PNode

* Improve performance

* Improve performance

* Cleanup

* Fix #17025

* Grammar

* Expand testcase

tests/arc/t17025.nim

@@ -0,0 +1,56 @@
+discard """
+  cmd: "nim c --gc:arc $file"
+  output: '''
+{"Package": {"name": "hello"}, "Author": {"name": "name", "qq": "123456789", "email": "email"}}
+hello
+name
+123456789
+email
+hello
+name2
+987654321
+liame
+'''
+"""
+
+import parsecfg, streams, tables
+
+const cfg = """[Package]
+name=hello
+[Author]
+name=name
+qq=123456789
+email="email""""
+
+proc main() =
+    let stream = newStringStream(cfg)
+    let dict = loadConfig(stream)
+    var pname = dict.getSectionValue("Package","name")
+    var name = dict.getSectionValue("Author","name")
+    var qq = dict.getSectionValue("Author","qq")
+    var email = dict.getSectionValue("Author","email")
+    echo dict[]
+    echo pname & "\n" & name & "\n" & qq & "\n" & email
+    stream.close()
+
+main()
+
+proc getDict(): OrderedTableRef[string, OrderedTableRef[string, string]] =
+    result = newOrderedTable[string, OrderedTableRef[string, string]]()
+    result["Package"] = newOrderedTable[string, string]()
+    result["Package"]["name"] = "hello"
+    result["Author"] = newOrderedTable[string, string]()
+    result["Author"]["name"] = "name2"
+    result["Author"]["qq"] = "987654321"
+    result["Author"]["email"] = "liame"
+
+proc main2() =
+    let dict = getDict()
+    var pname = dict.getSectionValue("Package","name")
+    var name = dict.getSectionValue("Author","name")
+    var qq = dict.getSectionValue("Author","qq")
+    var email = dict.getSectionValue("Author","email")
+    echo pname & "\n" & name & "\n" & qq & "\n" & email
+
+main2()
+