cmComputeLinkDepends: Convert AddLinkEntries to a template

Allow the method to be called with a vector of any type that can be
converted to cmLinkItem.
cmGeneratorExpressionEvaluator: Shorten some long lines

Adjust the definitions of getLinkedTargetsContent to avoid long lines.
cmTarget: Refactor LinkImplementation to allow more information

Create a cmLinkImplItem class derived from cmLinkItem so more
information can be added to link implementation entries than link
interface entries.  Convert the LinkImplementation Libraries member to
hold it.  Update client sites accordingly.
cmTarget: Add to LinkImplementation a backtrace for each library

Allow clients to provide backtrace context on evaluation diagnostics.
cmTarget: Add method to add usage requirements from linked interfaces

Create a cmTargetInternals::AddInterfaceEntries method to construct a
$<TARGET_PROPERTY:tgt,INTERFACE_XYZ> generator expression and evaluate
it for every target in the link implementation.  This will be useful to
de-duplicate such evaluation for each usage requirement separately.

The new method will soon be used in the implementation of the
INTERFACE_* usage requirement lookup methods (GetSourceFiles,
GetCompileOptions, GetCompileDefinitions, GetCompileFeatures,
GetIncludeDirectories).  It is necessary for these methods to determine
whether an expression in LinkImplementationPropertyEntries evaluates to
a target or not because generator expression evaluation reports an error
for non-targets and we construct a $<TARGET_PROPERTY:tgt,INTERFACE_XYZ>
expression for each entry that is a target.

The implementation of each usage requirement currently processes the
LinkImplementationPropertyEntries and evaluates all generator
expressions to determine targets.  That is no longer necessary because
GetLinkImplementationLibraries now returns resolved and cached targets
together with their name.  Use it to implement AddInterfaceEntries.
cmTarget: Simplify INTERFACE_SOURCES usage requirement lookup

Use the AddInterfaceEntries helper to avoid duplication.
cmTarget: Simplify INTERFACE_COMPILE_OPTIONS usage requirement lookup

Use the AddInterfaceEntries helper to avoid duplication.
cmTarget: Simplify INTERFACE_COMPILE_DEFINITIONS usage requirement lookup

Use the AddInterfaceEntries helper to avoid duplication.
cmTarget: Simplify INTERFACE_COMPILE_FEATURES usage requirement lookup

Use the AddInterfaceEntries helper to avoid duplication.
cmTarget: Add to LinkImplementation whether each library was a genex

Implementation of CMP0027 OLD behavior needs to know whether each entry
in LinkImplementation::Libraries came from a generator expression or
not.  Add a FromGenex member to cmLinkImplItem to record this.
cmTarget: Simplify CMP0027 logic in processIncludeDirectories

Evaluate and lookup the target name only once per TargetPropertyEntry
instead of repeating it for each include directory entry.  Use a local
checkCMP0027 variable to record whether the policy should be checked.
Evaluate the target name as a generator expression only if it looks like
one.  Lookup the target by name only after evaluation of generator
expressions.
cmTarget: Simplify INTERFACE_INCLUDE_DIRECTORIES usage requirement lookup

Use the AddInterfaceEntries helper to avoid duplication.  In
TargetPropertyEntry, replace the TargetName string member with a
reference to the full cmLinkImplItem that produced the entry.  This is
possible because the cmLinkImplItem is available in AddInterfaceEntries
(it was not available in GetIncludeDirectories).  Having the full
cmLinkImplItem allows processIncludeDirectories to implement CMP0027 OLD
behavior without repeating the target name lookup.

Update the RunCMake.CompatibleInterface test DebugProperties case
expected output for the new order of the messages.
Merge topic 'refactor-usage-requirement-evaluation' into next

3c8f6b1d cmTarget: Simplify INTERFACE_INCLUDE_DIRECTORIES usage requirement lookup
e77a094d cmTarget: Simplify CMP0027 logic in processIncludeDirectories
ba76e7ef cmTarget: Add to LinkImplementation whether each library was a genex
fd021b9f cmTarget: Simplify INTERFACE_COMPILE_FEATURES usage requirement lookup
361f99b5 cmTarget: Simplify INTERFACE_COMPILE_DEFINITIONS usage requirement lookup
36c4c139 cmTarget: Simplify INTERFACE_COMPILE_OPTIONS usage requirement lookup
586ff5f3 cmTarget: Simplify INTERFACE_SOURCES usage requirement lookup
3843c41f cmTarget: Add method to add usage requirements from linked interfaces
81f1bfe2 cmTarget: Add to LinkImplementation a backtrace for each library
2cf120cf cmTarget: Refactor LinkImplementation to allow more information
0e9f7a1e cmGeneratorExpressionEvaluator: Shorten some long lines
3cb21f27 cmComputeLinkDepends: Convert AddLinkEntries to a template