Fix cross-file navigation features when #line is used

[dsyme]

This fixes

• Find References doesn't work if #line directives are used  #9928

This is about how VS and FCS behave when #line is used.

This PR makes sure no line directives are applied for the incremental build, for the VS IDE, which now passes the hidden flag --ignorelinedirectives, similar to other hidden flags we pass such as --vserrors. The same technique as #6004 is used - that is, the IDE directs the background build not to take line directives into account.

Note some clients of FCS (e.g. Fable) definitely do want to take #line into account (because they are implementing a compiler).

Desired specification

In general, the VS IDE should ignore #line. The current status for F# before this PR is

• GOOD: colorization works
• GOOD: brace matching works
• GOOD: diagnostics-from-build are reported and take #line into account
• GOOD: diagnostics-from-intellisense are reported and do not take #line into account
• GOOD: #nowarn works in generated source
• GOOD: autocomplete works at all in generated source
• GOOD: tooltips work in generated source
• GOOD: goto-definition works in generated source
• FIXED BY THIS PR: diagnostics when using --ignorelinedirectives
• FIXED BY THIS PR: goto-definition doesn't work across files
• FIXED BY THIS PR: find-all-references doesn't work at all
• FIXED BY THIS PR: bug #nowarn in the editor does not ignore warning if --warnaserrors flag is set, but compiler does #9796

[KevinRansom]

oh it's not against main. :-)

[dsyme]

This is now ready