docs: replace `FOO by :term:FOO` where possible

If a variable has a glossary entry and some rST files write about those
variables, it's better to point to the glossary entry instead of just
highlighting it by surrounding it with two tick quotes.

This was automated by the following python script:
"""
import re
from pathlib import Path

with open('objects.inv.txt', 'r') as f:
    objects = f.readlines()

with open('bitbake-objects.inv.txt', 'r') as f:
    objects = objects + f.readlines()

re_term = re.compile(r'variables.html#term-([A-Z_0-9]*)')
terms = []

for obj in objects:
    match = re_term.search(obj)
    if match and match.group(1):
        terms.append(match.group(1))

for rst in Path('.').rglob('*.rst'):
    with open(rst, 'r') as f:
        content = "".joing(f.readlines())
    for term in terms:
        content = re.sub(r'``({})``(?!.*\s*[~-]+)'.format(term), r':term:`\1`', content)

    with open(rst, 'w') as f:
        f.write(content)
"""

(From yocto-docs rev: ba49d9babfcb84bc5c26a68c8c3880a1d9c236d3)

Signed-off-by: Quentin Schulz <foss@0leil.net>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reviewed-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/migration-guides/migration-1.4.rst

@@ -28,7 +28,7 @@ Differences include the following:
    and uninstall script functions ``pkg_preinst``, ``pkg_postinst``,
    ``pkg_prerm``, and ``pkg_postrm`` should always have a package name
    override. For example, use ``RDEPENDS_${PN}`` for the main package
-   instead of ``RDEPENDS``. BitBake uses more strict checks when it
+   instead of :term:`RDEPENDS`. BitBake uses more strict checks when it
    parses recipes.
 
 .. _migration-1.4-build-behavior:
@@ -53,10 +53,10 @@ Differences include the following:
    :term:`SRC_URI`, the build system now uses
    :term:`FILESOVERRIDES` instead of
    :term:`OVERRIDES` for the directory names. In
-   general, the values previously in ``OVERRIDES`` are now in
-   ``FILESOVERRIDES`` as well. However, if you relied upon an additional
-   value you previously added to ``OVERRIDES``, you might now need to
-   add it to ``FILESOVERRIDES`` unless you are already adding it through
+   general, the values previously in :term:`OVERRIDES` are now in
+   :term:`FILESOVERRIDES` as well. However, if you relied upon an additional
+   value you previously added to :term:`OVERRIDES`, you might now need to
+   add it to :term:`FILESOVERRIDES` unless you are already adding it through
    the :term:`MACHINEOVERRIDES` or
    :term:`DISTROOVERRIDES` variables, as
    appropriate. For more related changes, see the
@@ -105,7 +105,7 @@ Variables
 
 The following variables have changed:
 
--  ``SANITY_TESTED_DISTROS``: This variable now uses a distribution
+-  :term:`SANITY_TESTED_DISTROS`: This variable now uses a distribution
    ID, which is composed of the host distributor ID followed by the
    release. Previously,
    :term:`SANITY_TESTED_DISTROS` was
@@ -114,7 +114,7 @@ The following variables have changed:
    you are not specifically setting this variable, or if you are
    specifically setting it to "".
 
--  ``SRC_URI``: The ``${``\ :term:`PN`\ ``}``,
+-  :term:`SRC_URI`: The ``${``\ :term:`PN`\ ``}``,
    ``${``\ :term:`PF`\ ``}``,
    ``${``\ :term:`P`\ ``}``, and ``FILE_DIRNAME`` directories
    have been dropped from the default value of the