RFR: 8301564: Non-C-heap allocated ResourceHashtable keys and values must have trivial destructor [v2]

[Ioi Lam]

> To ensure we don't have memory leaks or other more serious memory management bugs, I added static asserts to check that the `K` and `V` types for `ResourceHashtableBase` must have trivial destructors if the table is not `C_HEAP` allocated. Thanks to @JornVernee for the original assert code.
> 
> The asserts actually found a problem with `ClassLoaderStatsClosure::StatsTable`. The space used by the `oop` in the freed hashtable may be trashed when `-XX:+CheckUnhandledOops` is enabled, so live objects that reuse the same space may be corrupted. (I tried but couldn't get it to fail).
> 
> I also had to change `CodeBuffer::SharedTrampolineRequests` because it's `V` type is `LinkListImpl<int>`, which has a non-trivial destructor. (Note: in this case, the destructor doesn't do anything; we can probably make it go away with C++-20. See https://stackoverflow.com/questions/40094871/sfinae-away-a-destructor)
> 
> Testing with tier1~4 + builds-tier5

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @coleenp comments - use mtStatistics instead

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12355/files
  - new: https://git.openjdk.org/jdk/pull/12355/files/e3ccac72..915f058b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12355&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12355&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12355.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12355/head:pull/12355

PR: https://git.openjdk.org/jdk/pull/12355