big steps torwards an efficient, simple IC implementation (#16543)

* reworked ID handling
* the packed AST now has its own ID mechanism
* basic serialization code works
* extract rodfiles to its own module
* rodfiles: store and compare configs
* rodfiles: store dependencies
* store config at the end
* precise dependency tracking
* dependency tracking for rodfiles
* completed loading of PSym, PType, etc
* removed dead code
* bugfix: do not realloc seqs when taking addr into an element
* make IC opt-in for now
* makes tcompilerapi green again
* final cleanups

Co-authored-by: Andy Davidoff <github@andy.disruptek.com>

compiler/modulegraphs.nim

@@ -9,7 +9,7 @@
 
 ## This module implements the module graph data structure. The module graph
 ## represents a complete Nim project. Single modules can either be kept in RAM
-## or stored in a Sqlite database.
+## or stored in a rod-file.
 ##
 ## The caching of modules is critical for 'nimsuggest' and is tricky to get
 ## right. If module E is being edited, we need autocompletion (and type
@@ -26,7 +26,7 @@
 ##
 
 import ast, intsets, tables, options, lineinfos, hashes, idents,
-  incremental, btrees, md5
+  btrees, md5
 
 # import ic / packed_ast
 
@@ -67,7 +67,6 @@ type
     intTypeCache*: array[-5..64, PType]
     opContains*, opNot*: PSym
     emptyNode*: PNode
-    incr*: IncrementalCtx
     canonTypes*: Table[SigHash, PType]
     symBodyHashes*: Table[int, SigHash] # symId to digest mapping
     importModuleCallback*: proc (graph: ModuleGraph; m: PSym, fileIdx: FileIndex): PSym {.nimcall.}
@@ -176,7 +175,7 @@ proc stopCompile*(g: ModuleGraph): bool {.inline.} =
   result = g.doStopCompile != nil and g.doStopCompile()
 
 proc createMagic*(g: ModuleGraph; name: string, m: TMagic): PSym =
-  result = newSym(skProc, getIdent(g.cache, name), nextId(g.idgen), nil, unknownLineInfo, {})
+  result = newSym(skProc, getIdent(g.cache, name), nextSymId(g.idgen), nil, unknownLineInfo, {})
   result.magic = m
   result.flags = {sfNeverRaises}
 
@@ -190,7 +189,7 @@ proc registerModule*(g: ModuleGraph; m: PSym) =
 
 proc newModuleGraph*(cache: IdentCache; config: ConfigRef): ModuleGraph =
   result = ModuleGraph()
-  result.idgen = IdGenerator(module: -1'i32, item: 0'i32)
+  result.idgen = IdGenerator(module: -1'i32, symId: 0'i32, typeId: 0'i32)
   initStrTable(result.packageSyms)
   result.deps = initIntSet()
   result.importDeps = initTable[FileIndex, seq[FileIndex]]()
@@ -206,7 +205,6 @@ proc newModuleGraph*(cache: IdentCache; config: ConfigRef): ModuleGraph =
   result.opNot = createMagic(result, "not", mNot)
   result.opContains = createMagic(result, "contains", mInSet)
   result.emptyNode = newNode(nkEmpty)
-  init(result.incr)
   result.recordStmt = proc (graph: ModuleGraph; m: PSym; n: PNode) {.nimcall.} =
     discard
   result.cacheSeqs = initTable[string, PNode]()
@@ -235,7 +233,6 @@ proc dependsOn(a, b: int): int {.inline.} = (a shl 15) + b
 
 proc addDep*(g: ModuleGraph; m: PSym, dep: FileIndex) =
   assert m.position == m.info.fileIndex.int32
-  addModuleDep(g.incr, g.config, m.info.fileIndex, dep, isIncludeFile = false)
   if g.suggestMode:
     g.deps.incl m.position.dependsOn(dep.int)
     # we compute the transitive closure later when querying the graph lazily.
@@ -243,7 +240,6 @@ proc addDep*(g: ModuleGraph; m: PSym, dep: FileIndex) =
     #invalidTransitiveClosure = true
 
 proc addIncludeDep*(g: ModuleGraph; module, includeFile: FileIndex) =
-  addModuleDep(g.incr, g.config, module, includeFile, isIncludeFile = true)
   discard hasKeyOrPut(g.inclToMod, includeFile, module)
 
 proc parentModule*(g: ModuleGraph; fileIdx: FileIndex): FileIndex =