Fix direct comparisons with unshared basic heap types

[tlively]

Audit the remaining ocurrences of == HeapType:: and fix those that did
not handle shared types correctly. Add tests for some of the fixes;
others are NFC but clarify the code.

[kripken]

I bisected a fuzz bug down to this commit. Testcase:

(module
 (rec
  (type $3 (sub (func)))
  (type $2 (shared (func (param f32))))
  (type $11 (func (param (ref eq) f32 f64 (ref $2) (ref $3) (ref null $4)) (result f64)))
  (type $4 (sub final $3 (func)))
  (type $1 (sub (array (ref null (shared array)))))
  (type $10 (func (param f64 (ref struct)) (result (ref $2))))
  (type $9 (struct))
  (type $8 (func))
  (type $7 (func (param i64)))
 )
 (type $7_0 (func (param i64)))
 (table $0 269 269 funcref)
 (elem declare func $2 $3)
 (tag $tag$0 (param i64))
 (func $0 (type $8)
  (drop
   (call $1
    (f64.const 0)
    (struct.new_default $9)
   )
  )
 )
 (func $1 (type $10) (param $0 f64) (param $1 (ref struct)) (result (ref $2))
  (drop
   (call_indirect $0 (type $11)
    (array.new_default $1
     (i32.const 0)
    )
    (f32.const 0)
    (f64.const 0)
    (ref.func $3)
    (ref.func $2)
    (block $label$1 (result (ref $4))
     (br_if $label$1
      (ref.func $2)
      (try (result i32)
       (do
        (return
         (ref.func $3)
        )
       )
       (catch $tag$0
        (drop
         (pop i64)
        )
        (i32.const 0)
       )
       (catch_all
        (unreachable)
       )
      )
     )
    )
    (i32.const 0)
   )
  )
  (ref.func $3)
 )
 (func $2 (type $4)
  (nop)
 )
 (func $3 (type $2) (param $0 f32)
  (nop)
 )
)

$ bin/wasm-opt aa.wat -all --inlining-optimizing --roundtrip
[wasm-validator error in function 0] break type must be a subtype of the target block type, on 
(block $label$1 (result (ref $4))
 (drop
  (array.new_default $1
   (i32.const 0)
  )
 )
 (drop
  (f32.const 0)
 )
 (drop
  (f64.const 0)
 )
 (drop
  (ref.func $3)
 )
 (drop
  (ref.func $2)
 )
 (br $label$1
  (ref.func $3)
 )
)
Fatal: error after opts

[kripken]

That fuzz bug bisected to this, but this was not the culprit. It only made it easier to hit the bug. Fix for that issue: #6976