drcachesim/cache_simulator to support YAML-formatted configuration files

[DmitrySPetrov]

Currently self-written configuration file parser is used.
This format is very simple and is not convenient for big configuration files.
Suggestion: Use YAML format instead.

Pros:

• YAML format is more clear and readable, both single-line and multi-line,
• YAML format support various features like mappings and aliases which are useful to model real-world hardware, for instance, server multicore processors.

Cons:

• Extra 3-rd party dependency,
• API change.

Suggested implementation:

• Use third-party libfyaml parser to read configuration files,
• Mark current configuration file format as deprecated and suggest to use YAML-formatted configuration.

[derekbruening]

What about:

• Support for including one file in another, which may be very convenient for sharing configs: this may be quite messy with a space-sensitive format like YAML? JSON may be better here? The actual including might be done via a C preprocessor pass (which would also add comment support incl block comments which are not present in YAML or JSON).

[derekbruening]

Other choices considered in the past include protocol buffer text format. But we ended up rejecting that due to library complexities in supporting it.

We have a past proposal to extend the existing format which has not yet been implemented: I filed that as #7728. It addresses two issues: avoiding duplication in multi-core config files, and making it easier to sweep different configs via command line parameters.