[lldb-vscode] Send Selected Statistics Dump in Terminated Event

This patch will gather debug info & breakpoint info from the statistics dump (from `(SBTarget.GetStatistics())` func) and send to DAP in terminated event.

The statistics content can be huge (especially the `modules`) and dumping in full JSON can create delay in the IDE's debugging UI. (For more details, please read: https://github.com/llvm/llvm-project/commit/7bbd0fba986c241162b77b7e424ad82bc7e17b41 ). Hence, we will filter out large contents before returning it in terminated event.

It will keep all the metadata fields (those starts with "total"). For large contents, it uses the opt-out strategy. Currently it only removes the "modules" field. This way every time a new top-level field being added, we will be able to capture them from DAP log without changing lldb-vscode.

The DAP terminated event should look like
```
{
  "event":"terminated",
  "seq":0,
  "statistics": {
    "memory": <JSON string>
    "targets": <JSON string>, // it's a JSON array, breakpoints info included in each target
    <metadata_key: value> // pairs
  },
  "type":"event"
}
```

All the info above will be append to statistics field in the terminated event

Test Plan

Debugged a simple hello world program from VSCode. Exit debug session in two ways: 1) run to program exit; 2) user initiated debug session end (quit debugging before program exit).
Check DAP log and see both debug sessions have statistics returned in terminated event.

Here's an example when debugging the test program:

```
{"event":"terminated","seq":0,"statistics":{"memory":"{\"strings\":{\"bytesTotal\":1843200,\"bytesUnused\":897741,\"bytesUsed\":945459}}","targets":"[{\"breakpoints\":[{\"details\":{\"Breakpoint\":{\"BKPTOptions\":{\"AutoContinue\":false,\"ConditionText\":\"\",\"EnabledState\":true,\"IgnoreCount\":0,\"OneShotState\":false},\"BKPTResolver\":{\"Options\":{\"NameMask\":[56],\"Offset\":0,\"SkipPrologue\":true,\"SymbolNames\":[\"foo\"]},\"Type\":\"SymbolName\"},\"Hardware\":false,\"Names\":[\"vscode\"],\"SearchFilter\":{\"Options\":{},\"Type\":\"Unconstrained\"}}},\"id\":1,\"internal\":false,\"numLocations\":1,\"numResolvedLocations\":1,\"resolveTime\":0.002232},{\"details\":{\"Breakpoint\":{\"BKPTOptions\":{\"AutoContinue\":false,\"ConditionText\":\"\",\"EnabledState\":true,\"IgnoreCount\":0,\"OneShotState\":false},\"BKPTResolver\":{\"Options\":{\"Column\":0,\"Exact\":false,\"FileName\":\"/data/users/wanyi/llvm-sand/external/llvm-project/lldb/test/API/tools/lldb-vscode/terminated-event/main.cpp\",\"Inlines\":true,\"LineNumber\":5,\"Offset\":0,\"SkipPrologue\":true},\"Type\":\"FileAndLine\"},\"Hardware\":false,\"Names\":[\"vscode\"],\"SearchFilter\":{\"Options\":{},\"Type\":\"Unconstrained\"}}},\"id\":2,\"internal\":false,\"numLocations\":0,\"numResolvedLocations\":0,\"resolveTime\":0.23203799999999999},{\"details\":{\"Breakpoint\":{\"BKPTOptions\":{\"AutoContinue\":false,\"ConditionText\":\"\",\"EnabledState\":true,\"IgnoreCount\":0,\"OneShotState\":false},\"BKPTResolver\":{\"Options\":{\"Language\":\"c\",\"NameMask\":[4,4,4,4,4,4],\"Offset\":0,\"SkipPrologue\":false,\"SymbolNames\":[\"_dl_debug_state\",\"rtld_db_dlactivity\",\"__dl_rtld_db_dlactivity\",\"r_debug_state\",\"_r_debug_state\",\"_rtld_debug_state\"]},\"Type\":\"SymbolName\"},\"Hardware\":false,\"SearchFilter\":{\"Options\":{\"ModuleList\":[\"/usr/lib64/ld-2.28.so\"]},\"Type\":\"Modules\"}}},\"id\":-1,\"internal\":true,\"kindDescription\":\"shared-library-event\",\"numLocations\":1,\"numResolvedLocations\":1,\"resolveTime\":0.00026699999999999998}],\"expressionEvaluation\":{\"failures\":0,\"successes\":0},\"firstStopTime\":0.087458974999999994,\"frameVariable\":{\"failures\":0,\"successes\":0},\"launchOrAttachTime\":0.052953161999999998,\"moduleIdentifiers\":[94554748126576,94554747837792,94554747149216,139800112130176,139800112161056,139800112206064,139800112340224,139800112509552,139800112236528],\"signals\":[{\"SIGSTOP\":1}],\"sourceMapDeduceCount\":0,\"stopCount\":8,\"targetCreateTime\":0.00057700000000000004,\"totalBreakpointResolveTime\":0.234537}]","totalDebugInfoByteSize":1668056,"totalDebugInfoEnabled":3,"totalDebugInfoIndexLoadedFromCache":0,"totalDebugInfoIndexSavedToCache":0,"totalDebugInfoIndexTime":0.027963000000000002,"totalDebugInfoParseTime":0.34354800000000002,"totalModuleCount":10,"totalModuleCountHasDebugInfo":3,"totalSymbolTableIndexTime":0.056050000000000003,"totalSymbolTableParseTime":0.23930000000000001,"totalSymbolTableStripped":0,"totalSymbolTablesLoadedFromCache":0,"totalSymbolTablesSavedToCache":0},"type":"event"}
```

Differential Revision: https://reviews.llvm.org/D137665