diagnostics: introduce struct column_options

diagnostics: introduce struct column_options

Consolidate 3 fields in diagnostics::context and
diagnostics::column_policy into a new struct
diagnostics::column_options.

No functional change intended; reduces the number of public
fields in diagnostics::context.

gcc/c-family/ChangeLog:
	* c-indentation.cc (should_warn_for_misleading_indentation):
	Update for moving diagnostics::context::m_tabstop into
	diagnostics::column_options.
	* c-opts.cc (c_common_post_options): Likewise.

gcc/ChangeLog:
	* diagnostics/column-options.h: New file, adding struct
	diagnostics::column_options, taken from fields in
	diagnostics::context and diagnostics::column_policy.
	* diagnostics/context.cc (context::initialize): Update for moving
	fields of diagnostics::context into diagnostics::column_options.
	(column_policy::column_policy): Likewise.
	(column_policy::converted_column): Move implementation to...
	(column_options::convert_column): ...this new function.
	(context::report_diagnostic): Update for moving fields of
	diagnostics::context into diagnostics::column_options.
	(assert_location_text): Likewise.
	* diagnostics/context.h: Include "diagnostics/column-options.h".
	(class column_policy): Replace fields m_column_unit,
	m_column_origin, and m_tabstop with m_column_options.
	(context::get_column_options): New accessors.
	(context::m_column_unit): Move to struct column_options and
	replace with m_column_options.
	(context::m_column_origin): Likewise.
	(context::m_tabstop): Likewise.
	* diagnostics/sarif-sink.cc (sarif_builder::sarif_builder): Update
	for moving fields of diagnostics::context into
	diagnostics::column_options.
	* diagnostics/source-printing.cc: Likewise.
	* opts.cc (common_handle_option): Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>