On Windows SA agent gets a class vtable from symbols, exported from jvm.dll (it 
exports symbols like "??_7" + type + "@@6B@").
But symbol lookup function first requests WinDbg about the symbol.
Sometimes WinDbg routine IDebugSymbols::GetOffsetByName() returns offset for 
both class and class pointer types. Returned offsets correspond to symbols like 
"jvm!class_name::`vftable'".
The behavior is intermittent, I was not able to find what is the reason.
The fix adds workaround for the case - if GetOffsetByName succeeded, we check 
if corresponding symbol contains requested one.
So it returns expected offset for non-vtable symbols like "MaxJNILocalCapacity" 
(GetOffsetByName returns offset for "jvm!MaxJNILocalCapacity"), but returns 0 
for vtlb lookup.

Additionally added check for results of 
IDebugSymbols::SetImagePath/SetSymbolPath

Testing: tier1,tier2,hs-tier5-svc

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Commit messages:
 - windbg workaround

Changes: https://git.openjdk.org/jdk/pull/20684/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20684&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311993
  Stats: 22 lines in 1 file changed: 18 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/20684.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20684/head:pull/20684

PR: https://git.openjdk.org/jdk/pull/20684

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