Implementation of try_from_{nanos_u128,mins,hours,days,weeks}

[Zorbatron]

Implements the methods discussed in the related ACP. Closes rust-lang/libs-team#749.

impl Duration {
    pub const fn try_from_nanos_u128(nanos: u64) -> Result<Duration, DurationConversionError>;
    pub const fn try_from_weeks(weeks: u64) -> Result<Duration, DurationConversionError>;
    pub const fn try_from_days(days: u64) -> Result<Duration, DurationConversionError>;
    pub const fn try_from_hours(hours: u64) -> Result<Duration, DurationConversionError>;
    pub const fn try_from_mins(mins: u64) -> Result<Duration, DurationConversionError>;
}

ACP: rust-lang/libs-team#749
Tracking issue: #153678

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