[Upstream port] Add standard board examine, poll, reset, save_context functionality.

[EvgeniiDidin]

There is necessary to define standard target-specific functions, which are used by openocd during init process.

• Adding arc_configure function
• Adding arc_examine function
• Adding halt function
• Adding arc_poll function
• Adding arc_[de]assert_reset functions
• Adding arc_save_context function

[EvgeniiDidin]

Commit, adding arc_configure function:
fbb6f2e

[EvgeniiDidin]

Commit, adding arc_examine function:
543d6ca

[EvgeniiDidin]

Commit, adding arc_hatl function:
33a27db
Code of the function is based on:
https://github.com/foss-for-synopsys-dwc-arc-processors/openocd/blob/arc-2019.03-release/src/target/arc_dbg.c#L522

Unfortunately there is no commit message, so changes will be displayed here:

• Function is moved from arc_dbg.* to arc.* files.
• Code from arc_dbg_enter_debug moved inside arc_halt function
• Reworked printing additional debug information

[EvgeniiDidin]

Commits, adding arc_poll function:
88f427a
d191455
eb57a7a

Commit, adding arc_save_context function:
3fd1aa1