covoar keeps DWARF info in memory too long

[Alex White]

To get covoar working again, the ELF and DWARF info cleanup was moved from the ExecutableInfo constructor to the ExecutableInfo destructor. Without this change, covoar would report the locations of symbols as unknown:-1. This is because the DWARF info is used later in the ExecutableInfo::getSourceAndLine() method with a call to debug.get_source().

This caused a new issue: the ELF and DWARF info is now held in memory for the life of the program. This causes very high memory usage when running covoar, more than 10 GB for some BSPs.

A quick and dirty solution is to find what is being referenced in debug.get_source() and preserve it after debug.end() is called. It appears that refraining from calling cus.clear() in rld::dwarf::file::end() would be a good place to start. Additionally, the rld::dwarf::sources class will likely need to be changed to copy out the DWARF source file info.

[Alex White <alex.white@…>]

In a88be93/rtems-tools:

covoar: Store only the file name in ExecutableInfo?

This changes the ExecutableInfo? class to only store the executable
file's name rather than an entire instance of rld::files::object. This
allows the rld::files::object to be cleaned up in the ExecutableInfo?
constructor.

Updates #4383

[Alex White <alex.white@…>]

In ac56fce/rtems-tools:

covoar: Store address-to-line info outside of DWARF

This adds the AddressToLineMapper? class and supporting classes to
assume responsibility of tracking address-to-line information.

This allows the DWARF library to properly cleanup all of its resources
and leads to significant memory savings.

Closes #4383