fix(input.tail): Fix from_beginning option behavior

[wen-templari]

Summary

Currently, after setting from_beginning to true, tail will start from the beginning of the file regardless of the previous persisted offset.

This PR makes setting from_beginning to true only start from the beginning of the file when there is no persisted offset.

Checklist

• No AI generated code was used in this PR

Related issues

resolves #16237

[telegraf-tiger]

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Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[srebhan]

@wen-templari we cannot do this as this will likely break someone else's use-case where they want to enforce the start of file even if a state is persisted. I suggest we introduce a new option replacing from_beginning e.g. called read_start which can take the options

• end (default) - start reading from the end of the file
• beginning - start reading from the beginning of the file ignoring any saved offset
• saved offset or end - start reading from the persisted offset of the file or, if no offset persisted, start from the end
• saved offset or beginning - start reading from the persisted offset of the file or, if no offset persisted, start from the beginning

What do you think?