make var, let work in static, const sections (v2): without intermediate proc

[timotheecour]

EDIT: this still fail in some other tests...

alternative to nim-lang#18637

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fixes nim-lang/RFCs#276

see tests tests/misc/trfc_276.nim

static:

• fix [vm] Set/string/seq inside loop not initialized properly nim-lang/Nim#10938
• fix Top level variables inside loops are not reset in VM nim-lang/Nim#13312
• fix opcLdDeref (eg via addr) gives wrong results in inside static block nim-lang/Nim#13887

const:

• fix Const block variable memory being reused unexpectedly nim-lang/Nim#13918
• fix Error in const block inside proc nim-lang/Nim#12172
• fix Consts that call templates cannot evaluate whilst in procedure bodies nim-lang/Nim#13795

addr in static, const:

• fix addr doesn't work inside static at proc scope nim-lang/Nim#18641

note

• internal error in genRdVar in vmgen.nim  nim-lang/Nim#14645 is only partially fixed, another unrelated error remains, triggering: internalAssert(c.config, c.prc.regInfo[dest].kind < slotSomeTemp)