fix: reset _hasInputValue on programmatic input change (CP:14)

[mukherjeesudebi]

Description

Backports the following PRs:

• fix(date-picker): reset _hasInputValue on programmatic input change web-components#5625

Part of vaadin/web-components#5763

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[vursen]

Would it make sense to include vaadin/web-components#5645 directly in this PR?

[vursen]

One test is failing on iOS Simulator and I can't understand why:

iOS Simulator iphone 10.3 ✖ test/events.html » events » has-input-value-changed event » without value » with user input » should be fired when clearing the user input with Esc

  expected false to be true
    <unknown> at   AssertionError at /components/chai/chai.js:5260:0
    <unknown> at           assert at /components/chai/chai.js:259:0
    <unknown> at        <unknown> at /components/chai/chai.js:597:0
    <unknown> at      addProperty at /components/chai/chai.js:3951:0
    <unknown> at        <unknown> at events.html:110:0