Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

bhyve(4): Remove a double word in a source code comment

- s/the the/the/

MFC after: 3 days

bhyve: add nvlist functions for setting unset nodes

If an emulation uses those functions instead of set_config_value_node
or set_config_value, it allows the config values to get
overwritten. Introducing new functions is much more readable than
if else statements in the emulation code.

Reviewed by: khng
MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D33770

bhyve: clean up trailing whitespaces

Clean up trailing whitespaces. No functional changes.

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D33681

Refactor configuration management in bhyve.

Replace the existing ad-hoc configuration via various global variables
with a small database of key-value pairs. The database supports
heirarchical keys using a MIB-like syntax to name the path to a given
key. Values are always stored as strings. The API used to manage
configuation values does include wrappers to handling boolean values.
Other values use non-string types require parsing by consumers.

The configuration values are stored in a tree using nvlists. Leaf
nodes hold string values. Configuration values are permitted to
reference other configuration values using '%(name)'. This permits
constructing template configurations.

All existing command line arguments now set configuration values. For
devices, the "-s" option parses its option argument to generate a list
of key-value pairs for the given device.

A new '-o' command line option permits setting an individual
configuration variable. The key name is always given as a full path
of dot-separated components.

A new '-k' command line option parses a simple configuration file.
This configuration file holds a flat list of 'key=value' lines where
the 'key' is the full path of a configuration variable. Lines
starting with a '#' are comments.

In general, bhyve starts by parsing command line options in sequence
and applying those settings to configuration values. Once this is
complete, bhyve then begins initializing its state based on the
configuration values. This means that subsequent configuration
options or files may override or supplement previously given settings.

A special 'config.dump' configuration value can be set to true to help
debug configuration issues. When this value is set, bhyve will print
out the configuration variables as a flat list of 'key=value' lines.

Most command line argments map to a single configuration variable,
e.g. '-w' sets the 'x86.strictmsr' value to false. A few command
line arguments have less obvious effects:

- Multiple '-p' options append their values (as a comma-seperated
list) to "vcpu.N.cpuset" values (where N is a decimal vcpu number).

- For '-s' options, a pci.<bus>.<slot>.<function> node is created.
The first argument to '-s' (the device type) is used as the value of
a "device" variable. Additional comma-separated arguments are then
parsed into 'key=value' pairs and used to set additional variables
under the device node. A PCI device emulation driver can provide
its own hook to override the parsing of the additonal '-s' arguments
after the device type.

After the configuration phase as completed, the init_pci hook
then walks the "pci.<bus>.<slot>.<func>" nodes. It uses the
"device" value to find the device model to use. The device
model's init routine is passed a reference to its nvlist node
in the configuration tree which it can query for specific
variables.

The result is that a lot of the string parsing is removed from
the device models and centralized. In addition, adding a new
variable just requires teaching the model to look for the new
variable.

- For '-l' options, a similar model is used where the string is
parsed into values that are later read during initialization.
One key note here is that the serial ports use the commonly
used lowercase names from existing documentation and examples
(e.g. "lpc.com1") instead of the uppercase names previously
used internally in bhyve.

Reviewed by: grehan
MFC after: 3 months
Differential Revision: https://reviews.freebsd.org/D26035