ICU-21796 Rename bazel build files from BUILD to BUILD.bazel. This can

prevent conflicts when ICU users have their own BUILD files already.

diff --git a/icu4c/source/common/BUILD b/icu4c/source/common/BUILD.bazel
similarity index 100%
rename from icu4c/source/common/BUILD
rename to icu4c/source/common/BUILD.bazel

diff --git a/icu4c/source/data/unidata/norm2/BUILD b/icu4c/source/data/unidata/norm2/BUILD.bazel
similarity index 100%
rename from icu4c/source/data/unidata/norm2/BUILD
rename to icu4c/source/data/unidata/norm2/BUILD.bazel

diff --git a/icu4c/source/i18n/BUILD b/icu4c/source/i18n/BUILD.bazel
similarity index 100%
rename from icu4c/source/i18n/BUILD
rename to icu4c/source/i18n/BUILD.bazel

diff --git a/icu4c/source/stubdata/BUILD b/icu4c/source/stubdata/BUILD.bazel
similarity index 100%
rename from icu4c/source/stubdata/BUILD
rename to icu4c/source/stubdata/BUILD.bazel

diff --git a/icu4c/source/tools/gennorm2/BUILD b/icu4c/source/tools/gennorm2/BUILD.bazel
similarity index 100%
rename from icu4c/source/tools/gennorm2/BUILD
rename to icu4c/source/tools/gennorm2/BUILD.bazel

diff --git a/icu4c/source/tools/toolutil/BUILD b/icu4c/source/tools/toolutil/BUILD.bazel
similarity index 100%
rename from icu4c/source/tools/toolutil/BUILD
rename to icu4c/source/tools/toolutil/BUILD.bazel

diff --git a/tools/unicode/c/genprops/BUILD b/tools/unicode/c/genprops/BUILD.bazel
similarity index 100%
rename from tools/unicode/c/genprops/BUILD
rename to tools/unicode/c/genprops/BUILD.bazel

diff --git a/tools/unicode/c/genuca/BUILD b/tools/unicode/c/genuca/BUILD.bazel
similarity index 100%
rename from tools/unicode/c/genuca/BUILD
rename to tools/unicode/c/genuca/BUILD.bazel

diff --git a/vendor/double-conversion/upstream/BUILD b/vendor/double-conversion/upstream/BUILD.bazel
similarity index 100%
rename from vendor/double-conversion/upstream/BUILD
rename to vendor/double-conversion/upstream/BUILD.bazel