[lldb] Add symbol/table count into statistics (#136226)
# New stats
The following stats are added and are available in both "statistics
dump" command and in python API.
1. In summary:
1. Add `totalSymbolsLoaded`. The total number of symbols loaded in all
modules.
2. Add `totalSymbolTablesLoaded `. The total number symbol tables loaded
in all modules.
2. In each module's stats:
1. Add `symbolsLoaded`. The number of symbols loaded in the current
module.
# Example
Example `statistics dump` output:
```
(lldb) statistics dump
{
...,
"modules": [
{
"path": "/Users/<username>/demo/simple/a.out",
"symbolsLoaded": 6,
...
},
...
],
...
"totalSymbolTablesLoaded": 42,
"totalSymbolsLoaded": 32198
}
```
# Tests
**Manual test**: Built and ran lldb on a helloworld program. Ran
`statistics dump`. Verified the above stats.
**Unit test**: Ran the following tests:
```
$ bin/lldb-dotest -p TestStats.py ~/llvm-sand/external/llvm-project/lldb/test/API/commands/statistics/basic/
...
Ran 18 tests in 192.676s
OK (skipped=3)
```
