add file: support for RHOSTS option on exploit modules

[busterb]

This implements file: support for the RHOSTS option on exploit modules. Through a minor oddity with how the OptAddressRange option works, looking at 'RHOSTS' directly from the module returns the string literal rather than the normalized form. This PR instantiates an OptAddressRange if RHOSTS is specified for the purpose of normalizing file: back into the correct value.

Verification

• Start msfconsole
• use exploit/windows/smb/ms08_067_netapi or any remote exploit
• set RHOSTS single-ip
• Verify a single host is exploited
• set RHOSTS ip-range
• Verify multiple hosts are exploited
• set RHOSTS file:rhosts.txt
• Verify the contents of rhosts.txt is exploited
• use exploit/windows/fileformat/dvdx_plf_bof or any non-remote exploit
• ** Verify** the exploit works as expected

[wvu]

LGTM, will test and land after lunch.

[wvu]

Release Notes

This fixes a validation bug in setting RHOSTS via file: in an exploit.

[Green-m]

This patch works well, thank you @busterb.

And there is one more thing, not related to this PR, just for discussing.
This line of code aims at validating the option of exploit module, but it not supported for RHOSTS, to avoid bugs referenced in #11493 and this PR, we have to preprocess the option before entering the exploit_simple method.

metasploit-framework/lib/msf/base/simple/exploit.rb

Line 76 in 78605d5

exploit.options.validate(exploit.datastore)

What I want to say is, shall we plan to streamline the exploit/auxiliay procedure to make code more elegant and consistent? Even for better parallelised mentioned in #11318? At the beginning of the framework design, it did not consider for multiple threads and hosts during exploit.

[wvu]

That is a great idea, @Green-m.