[Chips] In MDCChipField, account for horizontal padding when calculating available width for text field

[bryanoltman]

This change addresses an issue introduced in #9837, where the calculation of available width for the text field did not take into account the chip field's horizontal insets.

[material-automation]

bazel detected changes to the following targets:

//components/Chips:Chips
//components/Chips:ObjcExamples
//components/Chips:SwiftExamples
//components/Chips:Theming
//components/Chips:privateHeaders
//components/Chips:snapshot_test_lib
//components/Chips:snapshot_tests
//components/Chips:snapshot_tests.swift_runtime_linkopts
//components/Chips:snapshot_tests_test_binary
//components/Chips:snapshot_tests_test_bundle
//components/Chips:unit_test_sources
//components/Chips:unit_test_swift_sources
//components/Chips:unit_tests
//components/Chips:unit_tests_IPAD_PRO_12_9_IN_9_3
//components/Chips:unit_tests_IPAD_PRO_12_9_IN_9_3.swift_runtime_linkopts
//components/Chips:unit_tests_IPAD_PRO_12_9_IN_9_3_test_binary
//components/Chips:unit_tests_IPAD_PRO_12_9_IN_9_3_test_bundle
//components/Chips:unit_tests_IPHONE_7_PLUS_IN_10_3
//components/Chips:unit_tests_IPHONE_7_PLUS_IN_10_3.swift_runtime_linkopts
//components/Chips:unit_tests_IPHONE_7_PLUS_IN_10_3_test_binary
//components/Chips:unit_tests_IPHONE_7_PLUS_IN_10_3_test_bundle
//components/Chips:unit_tests_environment
//components/Chips:unit_tests_environment.swift_runtime_linkopts
//components/Chips:unit_tests_environment_test_binary
//components/Chips:unit_tests_environment_test_bundle
//components/schemes/Shape:ObjcExamples