[WIP] [testament] compile/run compiler/**

[timotheecour]

before PR:

• not all compiler sources are used when building nim from compiler sources
• isMainModule tests in compiler sources are not actually being tested

after PR:

• same treatment as stdlib
• helps find dead code automatically (eg compiler/canonicalizer.nim doesn't seem used anymore, and doesn't compile)
• helps find/fix issues eg:
  replaced assert st.getOrDefault("www.harvardsucks.com") == nil to == "" to make compiler/btrees.nim pass

other changes in this PR

• now show action (eg : run/compile etc) in PASS/FAIL msgs eg:
  PASS: compiler/bitsets.nim C compile ( 1.56246400 secs)

note

• currently slow, may need to use technique described here stdlib modules should run via megatest (or megatest_stdlib), with special isMainModule handling #10045 to speed up
• currently, not including "compilerlib" in "all" category to avoid this slowness but can be run locally

[Araq]

I'd rather do it my way.