[Linux][GDB-JIT] Fix bugs in gdbjit that break lldb stepping (dotnet/coreclr#8637)

[Linux][GDB-JIT] Fix bugs in gdbjit that break lldb stepping (dotnet/coreclr#8637)

* Fix .text and .thunk symbols overlapping

When current method calls itself, a __thunk* symbol might be generated with the same address
as the method symbol in .text section. Avoid generating such __thunk* symbol.

* Do not create DWARF line table entries with the same address

* For each HiddenLine assign a zero line number in DWARF

Allow LLDB to to skip HiddenLines when stepping.

* Fix __thunk symbols containing garbage

Fix a bug when __thunk* symbols of previously compiled methods cause
generation of __thunk* symbols for currently compiled method without
filling symbol info.

* Fix missing check for the end of list of compiled methods

* Remove unnecessary check for zero prevLine in gdbjit

Commit migrated from https://github.com/dotnet/coreclr/commit/d23b78ce50d04e97cc23f997fab8c0ce5faa8726